Never been a Sid user (occasionally for specific packages) but I do find articles like these amusing - for me the transition from testing to stable is usually where I say goodbye to a Debian release. So farewell Trixie! Onto forky I go.

I’ve had a few instances of X not starting, over the years. Nothing terrible, and that’s as much down to me using nvidia cards as anything.

Lots of Debian Developers run unstable, and stable gets the most QA, but I'd be careful about running testing until it gets closer to the next freeze. When I used to daily drive testing, there was a period when it was completely broken. Stable and unstable were fine, but testing was borked.