Haven’t read all the posts here, but in my experience:
Sierra --> High Sierra: Immediately, without a doubt. Brings waste improvements to the iCloud sync, in case you are using it, and removes quite some annoyances from Sierra. Some folks are reporting issues on the AppleScript level, though.
High Sierra --> Mojave: Well, don’t know. I updated 3 weeks after the release, and I don’t notice any deteriorations since then. If you like Dark Mode, it’s a no-brainer, likely. Otherwise, I think the major improvement is the update of APFS, which now works with Fusion Drives, and all external hard disks, i.e. non-SSDs. (Maybe the latter has been true also before, not sure, but I converted my external HDs only now (with Mojave) to APFS.)
As a rule of thumb:
On macOS I would always update to the current OS version (not to the beta). One reason for that are the security patches, which are first and foremost applied to the current version. (Usually, if the thing is important, it is also applied to legacy OS versions. But I wouldn’t swear on it.)
But, before updating, check the Mac user forums, the user forums of specific apps (like this one), and the developer forum. Especially in the latter one you’ll find hints, if an update poses major problems.
Always up to you to judge if the potential issues outweigh the benefits. Usually they don’t, and issues tend to be hyped.
If still in doubt: update to the current version (not the beta).