A mate of mine got a 550D (with the IS kit lens at least), after borrowing my 50/1.8 for about half an hour he was convinced to buy one.
Even wide-open he's happy enough with the results, but then he uses it like me, only for night/gig/indoors shots, where it's a choice between 50@1.8, kit lens at 1/4s, or kit lens at iso6400, niftyfifty wins every time.