Bit the bullet and tried this myself.
Machine being used: Windows Vista Ultimate, 64bit, Service Pack 1
I uninstalled ALL Phatnoise software, rebooted
Installed Phatnoise Music Manager 1.87 from CD. When it got to the "installing additional software", I overwrite the existing AT&T Natual Voices .msi in C:\Program Files (x86)\PhatNoise Music Manager with the hacked on I found on the forum. This allowed Natural Voices to install under VIsta. Then I rebooted after install
I then when through a continual update process. Next I installed Music Manager 2.30. This performed an upgrade and it noted this in the installer, then rebooted. Then I did Media Manager 3.76. This installed side-by-side with Music Manager as opposed to doing an upgrade, but it did retain my registration key and use of AT&T Natural Voices. I had to modify the registry and add the Reg_Status key and set to 2. Lastly I installed Media Manager 3.92 and rebooted, and that's where I'm at today.
If I were to do it again, I'd go straight from Music Manager 1.87 from my CD, to Media Manager 3.92. I see no reason to do the incremental upgrades.
I had to make NO changes for application compatibility on PMM.EXE. Everything works flawlessly. I have the USB2 cradle and I needed no drivers. Copy speed seems to be pretty decent overall.