Another 50D fan checking in. My progression was 400D>40D>50D. The 50D took a while to come to terms with. After that, it is purely a great camera. It has nice AF performance, speed, microfocus adjust (important), build, CF memory, great LCD, and standard control layout (great ergos). Its image quality is great, ISO performance fine (with Canon's DPP to remove noise). When paired with great glass, the file detail is fantastic.
I shoot a 5D2 at work. It feels like a slug compared to the 50D. To be honest, the 5D2 is a great camera but I actually prefer the 50D for most shooting.
The 50D upgrade is the 7D, not the 60D. The thing is, I am so satisfied with the 50D that my next upgrade will have to wait for the 7D MkII. BTW, my 40D sits in the bag unused most of the time. It has crossed my mind to have it converted to IR.
Once I really came to terms with it, I am continually amazed with what the 50D can do. Here are a couple of high ISO images (DPP for automatic NR) as examples...
ISO6400 Test Shot
Real World image, ISO3200, 1/4 sec @ f/2.8, lens 17-55IS, Inside a coal mine!