On the heel's of a review of the HD-800, DAP Review has justed posted a new review of the DMC X-Clef 500:
Overall, I'm pretty happy with the HD-500. I love the 80gb worth of storage, the big screen, and simple GUI. It sounds excellent, and it's been running at least 12 hours per charge. FM radio and voice recording and useful features to have. The HD-500 has been valuable as an external hard drive as well, for backing up files and carrying them with me. I can hook it up to computers at work since I don't have to install software on them.
Of course, it's not all good. Compared to other DAPs, the HD-500 is big, heavy, and plain-looking. You can't search through music by iD3-tag catagories (Artist, Album, Title), and on-the-fly playlisting is limited. Recording quality is mediocre.
The HD-500 stands out the most for being a good value, if capacity is top on your list and you don't mind the size. The 40gb HD-500 ($230 at DigMind.com) costs about the same as the 30gb Nomad Zen, and the 80gb HD-500 ($380 at DigMind.com) is about the same price as the Zen Xtra 60gb, the iRiver iHP-140 (40gb), or a 20gb iPod.