Yea, I agree. You might first think that the sliding keyboard tray is a useful feature, but once you have a desk without it you realize its just a gimmick that makes life harder. Having a keyboard on it never usually leaves room for the mouse, the thing is so flimsy that usually it slides around and you end up not using it. Additionally, it usually makes it damn near impossible to mount a wheel onto the desk (you can try mounting it on the sliding tray, but even assuming it's sturdy enough to hold it, it moves ALL OVER the place and slides in and out.) I've had desks with and without them and I can tell you I'll never again get one with a sliding tray. They're just annoying. As James May would say, "It's an ingenious solution to a problem that should never have existed in the first place..."
... actually, I'm not quite sure if that quote applies 100%, but it gets my point across, and I've always wanted to say it :P