Installed the new 3.5.6 beta OS on Harmonizer, and new firewire driver on my desktop Mac running Lion. This was my first ever OS update on the Harmonizer, but it turned out to a smooth process. I smiled when the machine thanked me for releasing the #2 key.
Although I only have it up and running an hour now, all seems to work fine! My routings were still on the harmonizer and work as expected. I'll update here if I find anything unexpected.
Thanks for the update, Eventide. This means I can continue to work on my plan to go live with new macbook pro (with Lion pre-installed) + Harmonizer.