Rated 4 out of 5 stars
v0.9.5 was released on 2011/06/28 and IS compatible with FFx 5.0.1. Works well
Get it from the author's site:
Remember to check "Title before URL" and "Line break between entries"
If you don't check "Title before URL", there is no blank line between entries even if "Line break between entries" has been checked. Checking both options looks a lot neater IMO.
I suggest using UnMHT's "Save multiple tabs as MHT" option combined with CopyAllURLs.