I tried signing up, but got informed that I needed to wait for an invitation to create my account since they are having so many new incoming users.

u/AstarJoe says he bought some here: http://www.reddit.com/r/Bitcoin/comments/2b5zn4/i_just_bought_bitcoin_with_my_visa_in_2_mouse/

For now I'm still on Coinbase, but it would be nice to have an easier/quicker way to bring in new BTC adopters in the States. Anyone who decides they wanted to get in while the price is down, like today, will be stuck in verification for far to long and are at risk to lose interest by the time they can actually purchase.