Man, long time no vesrion 8 for me, but here's a few things to consider. I hope you've got a test environment to toy around in first =) Like any upgrade, I would recommend a full backup beforehand. Also check the QVS Reference Manual (PDF) as it has some upgrading considerations.
Licensing changes from v8 upwards - beginning with v9, there's no more Analyzer, Professional and Enterprise; just QlikView "Desktop." May want to talk to your account rep if you haven't already.
Upgrade all of your clients at the same time as the server, regardless of what any documentation says. I have NEVER had good luck using differing versions.
No more Java client, but I don't think anybody actually used that anyway..
I remember when going from 8 to 9 I had some small rendering issues, but nothing too terribly major. Oh, and my documents mostly origined back in v6 or v7, so this may not apply to you. Objects not lining up like they did before, or slightly different sizes, etc.
Publisher ~ I haven't had any success in upgrading Publisher, and I've done more than a couple upgrades. And the way Publisher tasks work is different after v8 (the job/task hierarchy.) I'd recommend you start clean setting up reloads etc. after the upgrade. Make sure you have your scheduling info etc. handy.
All for now ~ if more come to mind I'll repost. -Isaiah
the envoirment i'm planning to update right now has both 8.5 and 9.0 klients installed on the server that are running updates and sets variables through windows scheduler. can't really say why they've done this but that's what you by "Upgrade all of your clients at the same time as the server, regardless of what any documentation says. I have NEVER had good luck using differing versions." ?
Also i've heard that macros can be tricky if you're doin an upgrade. The macros in the documnets are basicly simple selects and exports of object, would that be a problem? Should i back up marcos beside backing up the hole server?