My path for updating the US Cellular based HTC Desire and Samsung Galaxy S Mesmerize.

Updating to Froyo wipes your phone settings completely.

Apps:

AppBrain
- Link AppBrain to your Gmail account
- Sync with AppBrain
- Log into the website with the account and verify you see all of your apps
Backup Everything
- Run Backup Everything on your phone
US Cellular Backup (for contacts)
- Run Backup

HTC Desire

http://www.uscellular.com/android/software.html (reference)
http://www.htc.com/us/support/desire-uscellular/downloads/ - Get the following
- HTC Sync 3.0.51 for HTC Desire™ | 01.11.2011 (69 MB)
- HTC Desire FROYO Upgrade (Software 2.11.573.0) | 02.08.2011
  - How to Download and Install (2 MB)
  - FROYO upgrade (Software 2.11.573.0) - Dowload (171 MB)
Install HTC Sync
Read the How To Download and Install
After you've updated AppBrain, Backup Everything, US Cellular Backup, connect the Desire to your PC and follow the How To Downland and Install directions
Phone reboots and finalizes 2.2
Setup phone initially as you when you first got it. Sign into everything you did before. Don't worry about Market updates
US Cellular Backup (for contacts)
- Run Backup to restore contacts
Go to the Market and get Backup Everything
- Restore your apps
  - I had SMS issues when I restored messages. Leave those out.
Go to the Market and get AppBrain
- Setup AppBrain and link to your Gmail account. Sync with AppBrain
- Go to the AppBrain website and look at your account
  - If there are no apps under your new phone's profile, move them from your old phone's profile
- Sync with AppBrain again & update programs
Once you are happy with Froyo, uninstall HTC Sync from your PC
Done

Desire with 2.2

Samsung Mesmerize

Waiting for US Cellular to get off its arse on this one...