I have both 50D and 7D.
Trust me, you should get that 7D!
7D:
8fps = awesome (i do sports photography some times)
19 focal points (Zonal focus points = best damn thing)
Also, 7D's focusing is way faster than the 50D's
and 7D's noise reduction is better than 50D's. (50D's noise is quite bad)
Hi TS, many of them here pointed out the good & bad about this comparison. Just think yourself, all those "good" do you really need it, and all those "bad" is it really bad for you? If you are using 300D right now, i advice you to go for 50D. 7D for me is just a short bridge for next level. I am sure within 2-3 years (or less) you will upgrade, Full Frame. Then you can go for 5DMkII. If really have budget, why don't you go for full frame straight away? Otherwise, save some $$ for accessories with 50D.
Just my own view. judge yourself.