M42 to Canon EF/EOS adapters

I mentioned it in another thread, but finally made the decision, and getting a 5DMK2 next week. There seems to be a lot of good longer glass (85, 135, etc...) in the M42 mount. I also already own a nice 50mm, and a very nice super takumar 35mm in M42 mount. Has anyone used the M42 to EF adapters, especially on a 5dMK2, any mirror issues, etc...