I posted to the MT forums about a couple problems I had after updating the templates yesterday.
I’m currently investigating the solutions, and have applied the one concerning “remember me”-cookies, with no luck. Maybe I have to clear my cookies first… The other one, with the empty preview forms, will likely have to wait for a final MT3 release. I’m not too keen on hacking my templates again, after spending quite some time on it yesterday. And I personally never preview my comments either.