Is the Preview For Developers (not the Tech Preview) pretty stable on the M8? I've only tried it on Lumia devices and I heard some of the horror stories from the ATIV SE...so just wanted to ask before I click the check mark.
Although the Preview for Developers right now has only very minor updates over the already fairly-up-to-date M8 for Windows (which shipped with 8.1 Update 1 already), so it probably won't cause any problems since there wasn't much that changed.
Although when 10 drops or potentially Update 2 (although I think it'll be skipped), I can't say.
I wouldn't do it yet. Stable or not, it does not really add any features yet worth "upgrading". Also, there is no official upgrade path yet nor is there an official way to revert back to 8.1 if you are not happy. I'm also betting that the soft keys stay lit and in view 100% of the time. That is a definite bug, not that there aren't others, and not that the bugs aren't expected, after all - it is a technical preview. I'd wait....