Hello,
Second post to tell you my experience with Dovecot 2 on Squeeze and to suggest a howto on it.
I installed it from the instructions here:
http://wiki.dovecot.org/PrebuiltBinaries#Debian
altho I installed it just fine, after I tried to install ISPConfig for obvious reasons it screwed up the config, so I manage to make it work with manual changes on the /etc/dovecot/conf.d/##-files but it'd be great if ISPConfig could determine Dovecot's version and proceed accordingly.
Thanks for this great project.