just wanted to pop in here and say I heartily recommend the following guide for further information about Dios Mios. I found it last night after DM didn't work for me (possibly a hard drive issue, haven't looked into it yet) and I was afraid I'd lost the ability to play gc games off the disc.
For the record, booting discs in CFG wasn't working, and neither was Gecko or any similar GC loader because they all require a working MIOS and I didn't make a backup of the original one.
I think some of the stuff in this guide should be added to GAF's official guide - for example I can confirm the MIOS that is given there restored complete functionality to my drive. I can play GC games from any region and with any video mode, just like I could before.
They are also working on a listing of harddrives that aren't compatible, as well as a games list.
http://www.wiihacks.com/other-faq-guides-tutorials/103429-guide-dios-mios-v2-0-a.html