The Gadget: Canon's 40D DSLR is their lower end prosumer DSLR, step above the Rebel series cams. It has, most notably a 10.1 megapixel rating and 3-inch LCD screen, Canon's latest DIGIC III processor and live view. I used the 30D and more recently the 40D for all Gizmodo's major liveblogging, so you've been seeing what the cam can do for some time now. (Which is also why I choose to shoot the cam sitting atop my messenger bag.)
Price: US$1499 with 17-85mm Image stabilised lens.
The Verdict: Compared to the 30D, the low light performance has been enhanced added noise reduction. (For the photography we find at trade shows and liveblogs, this is important.) The autofocus was generally faster but still sometimes wonky in low light, but the 3-inch LCD is extremely useful for field proofing. The CF door has new weatherproofing. Live view is kind of useless for me without autofocus. My biggest complaint is that the 40D is a little underwhelming compared to, say, the Nikon D300 with it's many more AF points and serious, serious low noise. (They're not really in the same class, if you ask Nikon and Canon reps, but I'd consider jumping up from the 40D to the D300.) And that the 18-85 lens has always been a bit soft for my liking. Can't explain it, but I've never found it to be as sharp as the 18-55 non-IS that came with the 30D. Those are my quick and dirty impressions (now updated with wisdom from the crowd below.)
AU: Wow. This is, um, kinda late. I've had a 40D since August last year... I didn't move up from a 30D, so can't comment on those comparisons, but I can say that it's an awesome camera for anybody looking to move up to a dSLR, or those that have come from a 400D (or similar) and want to take the next step.
And in case you're wondering, the 40D with lens is $2,299.