While a body with more functions may give a few more options, as a 1kD user I can safely say it has not failed me. Feel free to look at my portfolio... I believe that my pictures will speak for themselves.
I got the 1kD last year, so it was quite worthwhile due to price and the next highest. At this point however, the value of 550D is really too much to ignore, so if you can, probably it'd be better to toss in a little more and get a model that will probably last you all the way.
I am working towards a FF (either 5Dmk2/3 or 6D etc) and will probably stick to my 1kD... it is good enough for most basic use.
Welcome to CS: read, ask and snap =)