Expansion pass for me as well (which worked out quite well as December has other calls on my finances, although I would almost definitely still have found the money and pre-ordered anyway

).
I usually pre-order PDS content, but I literally haven't been disappointed with a Paradox expansion yet and want to support the devs as I've got more entertainment and other benefits from Paradox games than I have any other developer (by some margin). However, everyone's experience differs and one should only ever pre-order if they understand what it means and that's what they want to do (which is signalling demand and supporting the devs). There's very little immediate individual benefit to anyone from pre-ordering, particularly with expansions (unlike the games themselves, they don't have pre-order bonuses), and if you're not sure about the content, waiting until you can read some reviews (or play an MP game with a host that has the DLC, so you can give it a shake yourself and see what you think) is probably the safest option unless you've got a lot of disposable income so can afford to buy things that may or may not be for you.
Just for context for the thread, it's worth keeping in mind that pre-ordering expansions isn't some evil scheme by Paradox, it was apparently (I read a PDS post on this somewhere a little while ago) introduced in response to requests by fans.