Usually, portable ports of console games are really watered down versions; so you expect cut content alongside lowered performance and graphical fidelity. I was insanely surprised at this game though. I haven't played the console version of the game, but this version has a massive roster (35 characters), great graphics, and it runs really smoothly.
The character models look brilliant and have a lot of detail. The backgrounds look really impressive too, but are static, unlike the console versions.
The fighting system is standard Street Fighter; with a three buttons dedicated to punches and three buttons for kicks, representing light, medium and heavy attacks (Y, X and L for the punches and B, A and R for the kicks). Special moves are performed by certain directional inputs in addition to one of the attack buttons. On this 3DS version, you can also trigger a combo by pressing one of the four panels on the touch-screen. Usually D-Pads are preferred to control sticks in console fighting games, but the 3DS circle pad works well and is very comfortable to use.
You can practice combos in Challenge Mode where you are given the task of performing certain moves, or combinations of moves. Most moves can be extremely tricky due to the small time windows. It's hard enough pulling a lot of these moves off against a static opponent; and ends up close to impossible in the actual fights. The game does not automatically show you the button inputs either, so you have to go to the menu and choose Show Input to find out; which is terrible user experience.
In the Arcade mode, you are shown an animated cut-scene for an introduction sequence and ending sequence. Like most fighting games, the mode starts off really easy, but soon ramps up in difficulty, and is often insanely difficult when it comes to the final boss who has a great repertoire of moves; after-all he is like a hybrid of many of the characters.
With such a large character roster, this is going to take you an insane amount of time to work through the Arcade mode with each character, and I'm sure people will also spend time in the Challenge mode or playing multiplayer with their friends. As far as fighting game's go, I don't think you can get much better than this; especially on a hand-held. I do think it suffers from the same flaws as most fighting games, those being the high difficulty curve in Arcade mode, and the small time windows to input moves.