I refereed it, and I found I had more problems in about 2 years of futsal than 15 years of outdoor. Copped more pushes myself, and more extreme, over-the-top abuse. Just wasn't worth it in the end.
The problem with Futsal, at least in Melbourne, is that players have no accountability. Unlike outdoor, nothing happens to players who have done the wrong thing. Worst case scenario, they get banned from the centre so they play at the next one down the road. So even less respect than outdoor coupled with no accountability is a big problem.
The higher levels are fine, but it's the low grade, Tuesday night social stuff that was the real problem. Which is a shame because the game's a lot of fun to referee.
It can take a little bit of getting used to - for one, unlike outdoor, the player giving you a hard time is never more than 20 metres from you, so it does change how you have to manage the players. Two, it's viewing fouls - it's always a much more crowded space and you're limited to a side-on view, so it can take a bit of getting used to spotting the fouls in this environment.
The other nuisance is all the unwritten centre rules....I'd referee at one centre and apparently 'tackles from behind' are normally disallowed, as I'd find out when some bloke yells at me after somebody cleanly took the ball from behind. Go to another, players expect all instances of playing from the ground to be penalised, even when there's no risk. Stuff like that.