Combos
Their drive gauge system, and their choice to separate supers from it, has greatly enhanced the combo game. And not just what combos are possible, but more importantly, it forces players to make split-second decisions on which combo they want to do in a match in a way I don't think I've seen in a SF game before.
You'll be needing to judge whether you want to spend 0, 2 (EX), 3 (drive rush cancel, or EX + parry rush), 4 (two EX), or 5 (drive rush + EX) on your current combo. You'll also need to be judging whether you want damage, corner carry, or oki. And then you'll need to decide if you should be spending super or not, and how much. You might also be looking to sacrifice damage in your combo in order to strip your opponent of drive! For example, you could punish a blocked DP with drive impact crumple, followed by HP xx drive impact (which will strip 1 more bar from them and maybe burn them out).
Consider this situation: you have full drive and you block your opponent's DP and they have around 350 health left. You have half a second to decide your punish. Ideally, you want to kill them ONLY by using drive gauge, because this meter refills next round. Do you have a specific combo ready for this? What happens if you misjudge the health and you don't kill? Now you've maybe burned yourself out, dumping all your drive on a combo, and risk actually losing the round. So okay, maybe you just do a 3 drive punish and finish with level 2 super. This will easily kill, but you've wasted meter. Would level 1 super be enough? You don't have much time to think about this while playing.
There are "how do I spend my meter" decisions like this in other SF games, but nothing as complex as this, and I foresee a lot of really interesting decisions around BnB choice that aren't simply just "dump super and kill" or "do max damage meterless". Aggressive players will dump drive into their combos because they're confident they can control the opponent and gain the drive back before it matters, but sometimes they'll be wrong and that will be exciting. Conservative players will overspend super to ensure kills, rather than risk being wrong on the damage calculation, but they will sacrifice utility in the next round. Remember, you can "trade" spending your drive for spending your super in many combos, which means a stock of super meter actually means more neutral control since you can save drive for uses in neutral. But if you get caught in burnout, you'll be wanting super for defense, so you can't leave yourself with no super too often.
I've also come around on their cancel system. Level 1 supers can only be canceled off normals, nothing else. Level 2 supers can be normals or EX moves, while level 3 supers can be anything (including regular specials). At first I thought this would reduce possible cool combos, since I love doing DP xx super in SF games, and limiting that only to level 3 seemed a bit lame. But after playing, it's the right choice.
If you want to do cr.MK xx fireball and then cancel into super off this safe block string as an easy confirm, something that would be very strong due to how powerful pokes are, you have to spend level 3. That's it. There's no FADC or V-Trigger cancel that can help you convert this special move. If you want to lower the cost, you can spend 2 drive on a safe or plus-on-block EX during your pressure, and now you only have to spend level 2 on your confirm. If you could only spend level 1 on all these confirms, it would happen too often and its dominance would actually detract from all the interesting drive gauge decisions I outlined above.
Meanwhile, level 1 is far from useless. It's still useful in juggles and great at adding some small additional damage cashouts, but launching your opponent for a juggle usually requires something you can't easily confirm, or you have to spend drive gauge to cause the launch (for example, on drive rush to give you time to link into a heavy normal which has enough hit stun for your launching special move to combo). And, if you're low on drive gauge but want to deal damage, level 1s being cancelable off normals means your footsies are still scary, since you can whiff punish with cr.MK into super, very similarly to games like 3rd Strike.
I think the system comes together wonderfully on first blush. The decision making on which BnB to use will be considerably more varied than any past SF game, even once people dig into the combo theory and optimize it. My only hope, as I mentioned earlier, is that I really hope parry rush combos using the extra juggle points are worth the drive cost. I would like to see these combos often in matches and not just in combo videos.
Characters & Animation
I thought all the characters were pretty strong in the beta, but it's hard to tell their strengths and weaknesses until more time has been spent on the system and the effects of the plus frame changes, throws, and parry can be felt. I think Guile deserves a special mention as especially strong, given that his simple gameplan can be executed to its fullest in this game, especially while we're learning. He capitalizes on drive rush very well (a dash cancel mechanic that doesn't hate charge characters!) and has incredible space control with sonic booms, sonic blade and some very strong normals. Anti-airing neutral jumps from far away with drive rush feels super wild, but hopefully parry gives defenders a chance against sonic booms without having to jump.
The character often cited as the worst was Luke, but I totally don't see it; he has strong space control and good confirms, a +1 on block medium button, and feels like he plays with the SF6 systems well. Capcom should take a look at his level 2 super though, since it seems almost buggy with how short the range is (it often won't hit even when essentially point blank, and drops in many basic confirms that no other super in the game drops on). It's one of the better looking supers in the game, so I hope it's usable in the final game.
I think SF6 has a somewhat divisive animation style, but I've slowly grown accustomed to it. Most of the characters look quite good, I think, although there are still some outliers. I think Chun-Li in particular has lots of weird looking moves, which is a shame as she was one of SFV's best looking characters. From her chicken wing-looking st.MP, to her anti-air st.MK, to basically all of her stance moves, she just feels kind of "rubbery" and disjointed. I'm really hoping some touch-up work is done on her before launch. It's possible she was one of the first characters done in the SF6 style, because some of the presumably later characters look pretty good.
Two other things felt strange enough to mention here. I really don't like the throw tech animation. The pause at the start of the throw tech feels chunky, like the game is loading something, and then the characters kinda just slide to full screen instantly. It doesn't feel natural. The distance after a tech is not the problem here, but something needs to be done to make this whole process feel smoother. And maybe it's just me, but I felt the impact of Ryu/Ken/Luke's DPs felt strange in this game. Compared to Guile's flash kick, which sounds like a gunshot went off, the DPs just feel soft and not impactful, and it's not satisfying to finish a combo or anti-air with one. I'm hoping some combination of the hitstop or the sound effect is adjusted in the final release.