I've been using 40D for over 2 years. And I have to say (with reservations): Yes, I want to buy a 60D.
Everything is a compromise. Although I love me 40D, there are things that I always wish it have. Those things include pixel count, better LCD, video, better ISO performance, smarter button placement (putting everything underneath the LCD is just dumb), little lighter weight, and larger VF (man I love 5D's VF).
So is 60D a perfect camera for me? Of cause not. I hate the fact that Canon changed almost all the accessories (battery, grip, SD card, even cable release). But hell, the pros outweighs the cons.
I'm been living without AF micro-adjustment for some years, so that doesn't bother me a lot. I've been using a 350D for a while, so I know how plastic body feels like: not as solid as a magnesium body, but still acceptable. Is 5.3fps a huge problem? Ask those with a 20D or 30D.
So why not a 550D? I just can't live with the miniature grip and single dial control. And I can't say I like the small VF very much. Than how about Nikon? Sorry, not interested. My 70-200/4L IS and 50/1.8 are just adorable. Plus switching brand is just too costly.
In the end, it's all about what you really need and what you can live without.
EOS 40D+BG-EN3/350D/17-40 f4L/70-200 f4L IS/50 f1.8/18-55 f5.6/MacBook&ThinkPad