Well, 10.0 just came out. It is probably too early to say it's 100% safe, but I usually recommend upgrading after the first or second minor release.
I haven't heard of any major issues though, so there is that...
9.3 is definitely solid by this point. You might see some minor oddities in the 8->9 upgrade, but based on our experiences, they should be fairly minimal.
we are thinking of only upgrading the server at this point. Desktop upgrade will be done in the future. so yes
Tableau Desktop 8.2
Tableau Server 9.3.
Both these versions goes well together?
You may have asked this in another thread so sorry if this is repeat information. In earlier builds of Tableau Server if you upgraded your workbooks would automatically be upgraded to that same version. But we basically stopped doing this with version 9.0. So when you upgrade, your workbooks start out as still being 8.2.x but this could change for the following reasons:
(1) If someone uses webedit on Tableau Server and makes changes to the workbook and saves it, it will now be saved in the 9.3 format
(2) Should an end user jump the gun and upgrade to 9.3 and begin republishing workbooks or create new workbooks these would also be in the 9.3 format
An end user running Tableau Desktop 8.2 will not be able to open any workbook that was upgraded to the 9.3 format but your team may have control over when they get to upgrade Tableau Desktop and that could be a moot point.
It may have been stressed before but the best scenario would be to try this out in a non-Production environment first (eg DEV, UAT, etc). Please note that your Tableau Server EULA allows you one Production environment and two non-Production environments.