I like TradeHill but I think it could be a lot better than it is right now.
(for those who are from planet Mars, clic here to join TradeHill with a permanent discount)

1) Allow the users to choose in which currency they want their commission (and default it to Bitcoin!)

2) Allow user to sell/buy/instant sell/instant buy based on a number of dollars, not only bitcoin. Currently, if you want to empty your account to buy bitcoins, you have to do the math yourself

3) By the way, allow a quick function : sell everything or buy as much as I can in the instant buy/sell. That would be really helpful.

Thanks and Love :-)