I watched an online show of people playing this game before buying it for my girlfriend's birthday. Normally I play games like Ticket to Ride, Zombies and Seven Wonders, so this game was completely different, but so utterly engrossing. There were five of us playing it, and I think that's probably the least number of people you'd need. We had some cultural issues, with two players being English, two being Turkish, and one Colombian, and our various relationships meaning we could target our 'storytelling' to an individual. Mind you, that's half the fun.
You really need to play this game with creative and intelligent people. It's also a bit disappointing that you can only really have one layer of removal between your clue and the picture, once you go beyond that then you're really overassuming what people are able to do. There'll also be the problem of when my girlfriend and I next play this with a different group, as I presume we'll automatically be aware of what strange clues of ours can trigger the answer in the other. But we'll wait and see.
I'd probably also thoroughly recommend this game to families with children of 7 and up.. in fact, just give this game to a bunch of children and see how fascinating they are. The pictures are beautiful, but they should really provide you with more picture cards. We went through (revealed) about 85% of them in our first game.