We recently upgraded to 2.6.0.2 (yes, 2.6.0.2, not .03 like you asked) and have noticed some performance improvements on both 5220 and 5230 units. I will say that if you have *anything* custom and this is an upgrade from 2.5, make sure you have a copy of whatever it is off of the appliance and/or are ready to reinstall. This upgrade will also upgrade the OS and it does take awhile. Any other non-supported actions that have been taken may cause the upgrade to fail and rollback. We had created several users at the OS level vs using the CLISH commands and this caused us issues.
If your upgrade is from 2.6.0.1 or 2.6.0.2 you should be ok, but I would still make backups of any scripts or other items just in case.
Good luck,
-Rusty