Ok, update... I got a full backup working on the wife's computer. That is good news. Will need to try with another computer still as well as a restore and some other tests.
The bad news is that for some reason netatalk doesn't report the correct amount of free space on the DroboCapsule volume. By default, there is a bug in netatalk 2.2.1 where it is saying 0 free space (and the lead developer doesn't give enough of a sh*t about his bugs to help me figure it out).
I worked around that by reverting bits of the code to netatalk 2.1.x and now it is saying the drive is 100% empty even though I know there is data on it. Oddly, I think what is reported to TM and what is reported to the filesystem are two different values now. Ugh. So, I need to track that down before I feel comfortable with a release.
cheers,
jon