I'm another "just plain" user with a jb iphone, and I'm almost in the same place where Eoghann is:
I read here about the games here at TA and if they appeal to me, I try them, and if I like them, I buy. Sometimes I just buy them without trying first, as I did with Dead Trigger, Plague inc., Order & Chaos [what I buyed 2 copies: one for me and the other for my former gf]... also, I got Pocket Heros the released day, and I was so disapointed.
In the other hand, there are games that are already deleted from iTunes, as Earth Defender, so, what else you could do? You can't even buy them...
So, my PoV is near Eoghann's: Try & buy. iOS games aren't so expensive, and most of them are from small teams, so I feel glad of helping that [or you :P] guys, your works took me back to the gaming scene