Well I finally migrated yesterday given the impending deadline and then spent the next 2 hours cleaning up the mess. Had to remove 2 virtual hubs and nearly 70 virtual devices named either “sensor” or “meter” that I finally found out from another thread were because I’d used the IDE simulator in the past (which almost any developer will have done). Of course these simulator devices never appeared in Classic or in the IDE. Why anyone thought they should show up in the new app is a mystery.
I’ve also got what looks like a still-unresolved bug with location mode preconditions. Just seems to be plain broken.
Other than that the app performance is OK for me and I’ve mostly been able to get things back how I want them, with the exception of my virtual DTHs for Pollen and Air Quality. Having glanced at the new developer documentation it looks like they would require a near-complete rewrite, if I could even get them working at all. Given the still incomplete info there I have almost zero motivation to do that, especially combined with the changes on the roadmap to how SmartApps work. Hats off to those developers who are trying to stick with SmartThings but I am out as far as development goes.
Overall I give the new app 6/10. It’s not ready yet and they should not be retiring the Classic app while there are obvious automation bugs that have not been addressed. Combined with the lack of device filtering in the new Google Assistant integration, SmartThings has become considerably less polished in the last few months. I know there have been statements about how so much developer time is currently being eaten up triaging problems with the classic platform, and if they really do sunset the classic app next week as planned I hope they genuinely will be able to spend more time moving things forward again and get this mess straightened out.