They work great. I used a couple for quite awhile but briefly sold all my m4/3 gear. 2 weeks ago when the super cheap GH1/lens deal (check the off-brand sub-forum) came up I bought one, and got it yesterday. I also ordered
this adapter on ebay. Paid $2 for faster shipping and it only took a week!
The adapter is a nice build, and also has a small rod mechanism to control the aperture on DA lenses (or any others without an aperture ring). Last year I paid almost $60 for one that was cheaper build that did the same thing, so the one above was a steal.
The adapted lenses can be used in either A mode (camera will set shutter/iso speed) or full manual. As was noted above, focus is pretty easy, especially with the MF assist zoom.