This looked like an interesting thread from the title. It isn't. It's a dud.
Sure there are things to dislike about the 40D. Important things, some of them. Unfortunately, this thread doesn't seem to talk about them, instead we hear whining about the screen (who cares? the screen doesn't take pictures), the lack of ability of the spot meter to follow the AF point (a fair complaint, after all, most of us have probably owned $200 P&S cameras that do this, but hardly earth-shattering), flash synch speed (OK, I'll go along with that one too), poorly thought-out custom menus (yes, they could still use some work, though they are much improved on previous models), and (sigh) megapixels (hey, if you think more megapixels are the answer, buy a current generation P&S - they have way more MP per unit of sensor area. Megapixels don't mean diddly squat most of the time, once you are past 6 or 8.
Nevertheless, there are things that the 40D doesn't do nearly as well as it ought to do. I was looking forward to seeing a list of them all in one place, but it looks as though I'll have to write it myself. It's late and I'm past my bedtime, so I'll just jot down a few of the more obvious ones; maybe I'll come back and write a proper list another day.
1: The asinine ISO change method. What were they thinking? WERE they thinking at all? Sure, it's good to have a dedicated button for it, and good to show it in the VF all the time, but what on earth possessed them when they decided to put it under your finger instead of on the thumb wheel? No other Canon camera has the ISO there, and if you have more than one body, you will forever be fumbling for it, not just on the 40D, but on all your other bodies as well. Worse, it forces you to find the fiddly little button (different place to all the other Canons, of course), press it, and THEN move your finger to a different place to adjust it. Why? Why not have it on the thumbwheel like every other Canon so you can press with your finger and dial up or down with your thumb all in one motion?
2: The totally backwards aperture & shutter speed dials in manual mode. Normally, you have the aperture under your finger, and EC under your thumb. (If you shoot in Av mode, that is, which by far the majority of people do if they aren't shooting manual.) But switch to manual mode and - hey presto - everything is arsebackwards. Why? Again, what were they thinking? On the (older) ID III the factoory default is to do things backwards same as the 40D (or the 20D for that matter), but there is a custom function to put it back the right way around. No such function on the 40D, even though there are custom functions to do a whole slew of things that matter a good deal less. Are Canon determined to make the thing as difficult to use as possible?
3: No mirror lockup. Nothing more to say, it's inexcusable in a modern camera, especially one with so many buttons, several of them doing nothing in particular most of the time.
4: Failure to provide a genuine quick-change-to-common-settings mechanism. The "My Menu" feature is a step in the right direction, but has a long, long way to go before it's what it ought to be. The quick change feature ought to be a one-touch or at most two-touch function. Having it on a menu defeats the point.
Of course, there are things to like about the 40D too - it's an excellent camera in many respects and overall I'm happy with mine, it's just that it could be a whole lot better still, and should be a whole lot better.