Hey, I've gone to new versions of esx about 2-3 times starting from 3.5 to 4 etc........each time I started fresh.....But this was because I was usually going from old hardware to new (as vcenter wasn't recommended on VM previously). I also thought it was safer......I could completed screw up the install and not harm production. I've never had any issues with a fresh start.....but I also created a new DB(table only, not server). So I essentially had two running environments at the same time, when done. At this point, you can just transfer servers over by disconnecting from one and reconnecting to the next.
I've never have any trouble with vss or vDs. You just have to make sure the spelling and the Case is exactly the same on each, and everything should work find.
I now have 5.1 on VM and was thinking of trying to upgrade this time instead of going fresh to 5.5, which Is how I found this thread...... you are making me think twice though. I just felt the fresh start would be a little more in involved with the additions of sso etc.. How did you make out? did you continue with the upgrade? or start fresh?