OMG - Betsey Johnson 'Ditan' Pump floral

I love betsey johnson's line, I think her line is totally my style. So I've seen these shoes on the nordstrom site and been wanting them for every since. Urgh! Problem is that it runs 1/2 small. I don't really know what that means, but I want to get these for myself for my bday. Should I just risk it and by my usually size or buy one in 8 and 81/2, then returned the other?