Just a small note of caution for those joining in testing.
Currently the master branch has this issue where leveldb renames all of .sst files to .ldb. This makes running the 0.8.x version of Bitcoin think the index is corrupt. Until a fix is included in Bitcoin master, a workaround to allow 0.8.x to work again is to simply rename all the files from .ldb back to .sst.
(This workaround worked for me today but failed yesterday. It's possible I made an error yesterday. If it fails for you please report as we really need to know if there are other leveldb incompatibilities.)
The fix for Bitcoin's leveldb is being discussed here.
Warren