I'm running a couple of games right now with 2-3 players each session, it's usually 3 but occasionally someone can't show up and we play anyways. I won't say that it's perfect, but its not too bad at all. The players get alot of screen time and you have to be quicker on your improv because you'll get less break time as the MC with fewer players. But I still recommend it, players will advance quickly and enjoy all the focus they receive.
In contrast, as a player i've only ever played in games 4-6 players large and still had a great time. I'm in fewer scenes but it gives me a nice amount of time to think of what I want my character to do when it comes back to me, especially after a nice cliffhanger moment. Big groups or small groups both have their pro's and con's. What it basically comes down to for me is that I love this game so much I'll play alongside or MC any number of people, it's still gonna be a blast!