This is the closest thing that compares to Poker Tracker ( Which is in the windoze world )
It keeps track of your bankroll, your played hands, flops seen, VPIP, and other stats of yourself, and players at your tables.
The HUD works as planned, but currently the on table HUD only looks right on the default theme, as the boxes are not movable. The site does say movable boxes are in the works, though.
As for the price, compare this to other products with identical features in the Windoze world. I think it's reasonable. Most folks using this will be able to improve their game and see where some weaknesses are. Depending on what limits are played, it can pay for itself easily.
It's still missing some features as its counterparts, but the author seems to listen to peoples requests on their site