I've tried using it a fair bit on my 40D but I must admit that really can't be bothered any more. There's no contrast detection meaning that every live view shot has to be focussed manually by zooming in, focussing using the screen, zooming out, then taking the picture, I've found this to be at best a pain and at worst just plain impossible if you're close to the target (i.e. the slightest bit of forwards or backwards movement will put the camera out of focus).
There are SLRs with articulating screens but I've never really found a need for them that much. There's always the option to use an angle finder of course - like a little periscope in reverse that attaches to the eyepiece and allows the camera to be placed normally, but you look down into the angle finder eyepiece from above - it's at a right angle to the camera body. Hard to explain (for muggins here anyhow), easier to look up on t'internet, you'll soon see what I mean
