If you only come here for one thing, it should be that they have cheap nail polish. Essie, OPI, all the wonderful nail salon brands that cost you upwards of $10, will be a lovely $5-6 here!
As for everything else, they have decent selection, the store is kinda dingy looking inside but they carry decent brands of blowdryers and straighteners, and you'll get stuff for a little cheaper than you will elsewhere. I also like that you can get big bulk containers of salon shampoo and conditioner.
Unlike most Beauty Supply stores, this one is actually open to the public, so you can go in and browse without being asked you for your secret Haircutting Society card. But this place does ask you to register to buy certain items. As long as you stick to the cheap nail polish and shampoo, you don't have to show a card.