I'm trying to figure out what I've done wrong that mine is working when it sounds like it shouldn't be from reading these threads, LOL
Here is what, and ALL, I did.
1. I had gone back to stock because I thought I had to. Got PO'd because there wasn't an update on the 17th like we were told.
2. Went through the process of installing z4root and re-rooting my phone.
3. Installed ROM Manager (yeah, I know, don't bust my chops here) to get Clockwork Recovery installed so I could then get Amon Ra Recovery installed. After that - Bye Bye ROM Manager.
4. Installed Velocity v0.4 and did all the updates available in the Market.
NOTE: All those steps were on the 18th before I found out about the LGU version of FroYo.
5. Decided I couldn't wait until the ROM Gods cracked FroYo and decided to take my chances.
6. After a struggle with a recalcitrant firwall at work, I was able to get the update to download and install once I got home this morning (the 19th).
7. Loving FroYo, and finding that everything I usually run didn't require Root access anyway. Very Happy.

8. Read Indifferent's post, downloaded and flashed the recommended version of SU from his link. (I'm guessing I must have had the prior one required when I went to Velocity v0.4.)
9. Installed Root Explorer which I had previously purchased and was able to grant it Root access.
10. De-bloat-ified my Froyo.
11. Found a good program to move apps to the sdcard.
12. Encountered much satisfaction and joy.
Either I lucked out, or this really isn't as hard as it sounds.
Cheers - hope this helps someone.
One question: Couldn't people who went stock before they ran the update use Death's post
http://androidforums.com/ally-all-things-root/257859-unbrick-lg-ally.html to get back to 2.1 and then root, install a custom recovery and re-update to FroYo?