I've been using the hahnel grip with my 50D for over a year now and it's fine. Probably not quite as nicely built as the canon one as the buttons don't feel as 'solid' but still very good and a lot cheaper.
It comes with a battery tray like the canon one, so you can use AA's if you get stuck. It also has a little infra red sensor and remote shutter release which I tried on mine and it worked fine, although not used since as I have a chord release which i prefer.