actually I would wait with updating until QV9 is stable enough. We upgraded from 7.5 to 8.2 and then to 8.5. We faced the problem that from 7.5 to 8.2 (and of course to 8.5 there would be the same problem) suddenly an Enterprise/Developer licence was necessary for reloading. We always have been reloading by VBS/Batch on the server (standard publisher was no option for us due to several limitations - no macros, no passing of variables if I remember correctly). So my colleague's developer license had to be on the server from the time of upgrading to 8.2 until our upgrading to 9.0 several weeks ago meaning my colleague always had to work on the server....Not really sexy...
In QV 9 there is no difference between developer/professional/analyzer anymore.
In addition, we had several issues with registry keys and so on, so that it would have been better to DEINSTALL QV 7.5 as a whole and then newly install 8.X. Actually there were no issues concerning the upgrade procedere from 8.5 to 9.0.
That's just a few thoughts from memory ... perhaps it helps,