They are many shops still at DB2 V8 FP 6 (v8.1)…
The most important business risk is the out of service date. Check what is it currently on the website (or get in touch with IBM to get the info)
Other than that, if you can show that there will be cost advantage moving to a new level, management will be more than happy to support your efforts. Technical problems of the release level is hardly a convincing factor, if you are already on the release and have no problems.
Cost reasons to go to the later fixpaks could depend on the nature of the shop you are in ;
If you are aggressively developing new applications, there are umpteen new features in V8.2 that can be made use.
For admin type, there are a number of new features as well – eg. Activity monitor, enhanced health and event monitoring, automatic storage etc.
Go to the latest available fix level or the one before.
I understand that FP 10 and after are reasonably stable.
HTH
Sathyaram