TomMLS -- I personally prefer the clean install method.  However, I use VBS scripts to create my imaging jobs, and I store my images in date named folders.  The loss of the imaging job settings and history would not affect my scenario much.  If you go the upgrade route, then the following technote has some good info on troubleshooting a failed upgrade installation:

http://seer.entsupport.symantec.com/docs/317483.htm

How is an update actually possible? Cause live Update always tells me I got the newest version. Does the installation routine notice there is an older version?
It would kinda suck to make all the settings again on all the servers.

When uninstalling the product, there is usually prompting regarding completely removing the product, or leaving enough behind so that a new version install can salvage the image jobs.  The logical assumption is that the upgrade process is supposed to search for the image job locations even if the registry settings mentioned in the technote above are gone.  Since Symantec has owned this product, it has gone through four version series, i.e. 3.x, 6.x, 7.x,  and 8.x.  One would hope that they have standardized on user settings locations by now.

In the case of direct upgrade, the process is supposed to uninstall the previous version just enough to make importing the previous user setings  possible.  Luckily the job settings are not stored in the registry.

Perhaps the process has improved, but I opted to go the clean install route after too many failed upgrades.  I didn't lose any job settings, but as previously noted, those were taken out of the equation via VBS scripts.