This is by far one of the better flash adaptations of a street fighter game I've seen. The game stuck close to original Street Fighter moves and it the pocket sprites sure do look good.
I'm not concerned with the controls. I didn't find any hard time controlling them at all. My moves were executed almost at a 100% rate and as far as I'm concerned, you've managed to keep the controls relatively keyboard friendly. The one move that's close to impossible to pull off smoothly on a keyboard is the half circle or more. Quarter circle moves are very doable on the keyboard and I'm glad you stuck to that.
The 'Z' move is the slightly sketchy one though. It's not hard to pull off - it's just front down front - but it's hard to perform when I'm moving forward. To pull it off it requires stopping, tapping the front key again to begin the combo, and that made me avoid using those moves altogether. But the rest were fine. They were easy to do and very keyboard friendly compared to some direct ports which used much of the 'half circle' moves employed by arcade machines which are impossible on a keyboard.
What I find harder to do than just pulling off the moves is attempting old school SF combos that involve getting a hit and then immediately moving into a power combo. I found this quite hard to do in general and I'm thinking it could also be the 'recovery' time from a hit being a little too short. I've managed to get a very quick power combo in the moment I hit the opponent but they still managed to block it. The computer managed to do it to me though so I'm guessing one needs to execute the move perfectly with no delay, which can be quite tough to do when the time frame during the 'recovery' is so small.
Lastly, the powerups come by way too fast. The bars recharge way too easily - they charge both when hits are dealt and when gems are collected. Power combos also charge themselves too easily - they deal way too many hits and they generate such large gems sometimes that makes them never run out.
There are some damage balance issues that need to be worked out. I particularly think Ryu's spinning kick power combo deals way too many combo hits - 1 dealt combo = everything maxed out.
Aside from that, this is a good flash port of the game. I enjoyed playing a couple of rounds.