There’s a huge spectrum between different projects what’s meant with stable and not… So, I’m wondering how this is defined in Obsidian.
Basically, is it safe to use the insider builds for work? Cosmetic things being sometimes broken is fine (and I’m happy to contribute with reports), but crashes and losing data are not.
Well, no matter what I say here, this is just my lone experience. No matter what anyone says here about how stable it is: Always backup your important work. /PSA
It seems quite stable to me. I’ve only experienced cosmetic things, or mildly changed behaviours that eventually get fixed or a workaround. I think I’ve only seen Obsidian crash once and that was maybe a year or two ago. And I’ve never lost data. (But some people have. Most commonly - but not always - data loss seems to me to be related to cloud syncing. Or another open bug where some people have their note wiped, possibly from closing Obsidian quickly after an edit, or from a computer crash.)
If I ever do lose data, or have a plugin problem, I keep git snapshots so I can always roll back. (I don’t think I’ve ever had to roll back yet.) I snapshot my settings and notes separately. And I try to remember to commit a snapshot before upgrading or installing any plugins. I only use 9 to 12 community plugins. The more plugins you have installed, the higher chance you’ll have of experiencing cutting edge bugs.
Finally, I guess it depends what you mean by “for work”. Ask yourself how important your data integrity is. I’m just taking notes, studying material, and logging tasks for film and games. If you are in some extremely data-sensitive field, be extra careful!
Most of the problems I have seen are due to plugins failing. Time needed to update - occasionally it’s been a lot of time. If you don’t use many, and the ones you use are simple, you’ll probably never see a problem.
Next issue is workflow changes. Insider versions may have awkward or unfamiliar workflows. Smoothed over time as the new features are refined.
Thank you, I appreciate the info!
I have my vaults in Dropbox, so not worried about that side of things.
Another way to look at it, is that when the insider build is released it’s already been going through some testing within the developer team, and it’s presumed to be somewhat stable.
Or put another way, it’s not very fresh out of the oven, they’ve already used it a little internally within the developer team (I reckon). So it’s more like a mature beta version, than a bunch of new features piled together into an alpha version. At least this how I perceive the insider versions. 
I have found them extremely stable and routinely use them for work.