When I travel, I prefer to go to places that aren't the "well known" spots because they tend to be the most fun.
O'Sheas is fairly popular because it's on the strip but when you compare it to Mandalay Bay, Caesars, and other places it's not one of the more popular casinos.
I got raped at blackjack here, but hard to give a place a bad rating on that (I won a decent amount at Bill's Casino and wouldn't give that place 5 stars by any means). The biggest draw, however, is beer pong. We got a table fairly quickly and nobody was bugging us to get off of it. I know people don't go to Vegas to play beer pong, but we figured it would be a fun way to kill 3 hours and it was.