Everybody is going to have a different opinion on this, like everything else, but here is mine:
I don't use a sight on my gun, I prefer to look down the barrel. That being said, i'm looking to purchase a sight eventually to go with my new marker (just got a new cocker). I don't know what the difference will be, or whether I will like it or not. I will have to try it out and see.
I recommend you doing the same. If you can get your hands on (through borrowing, or buying a cheap one to test) then I recommend going that route. I've never really seen the need for using a site on a paintball gun, but I am beginning to. Even though there is a much wider variance in the flight of paintballs as apposed to real bullets, it may help in zeroing in on the target easier than looking at where the balls are going.
Let me know if you get a sight and how it works out, I would be curious to know myself.