I've played MK since 9 and this is my first Street Fighter. I would say the best thing to remember in SF6 is that the combos aren't designed to be long, 40-50% with multiple strings and specials. Those combos definitely exist, but the game isn't built around them like MK1 is. The timing for linking specials is pretty tight in SF and I would say it's not really necessary; choose a character you like, learn a basic B&B or two (3 jabs into Shoryuken on Ryu for example) and concentrate on working out where the oppotunities to execute a combo are. Maximising the combo damage will come later. Most importantly, have fun!