I'm no expert on this, but I've heard mixed stuff about the various Magic chips, and there are apparently a lot of crappy clones of it floating around. I don't recall hearing the the Magic V has any nasty problems, I think the last major incompatibilities were in the Magic III. The best chip overall seems to be the DMS3, but it's quite expensive and most people would probably not find much use for its unique features (loading apps from memory card, flash upgradable from CD-R w/write-protected backup, built-in support for Datel memory cards).
