[Dovecot] Differences between Versions 1 and 2?

What are the major differences between Versions 1.x and 2.0?

I am beginning to set up a new mail server for a small group of users (~20 accounts). Options are the "0.99" version pre- packaged with RHEL-4, or building v1.2.16 or v2.0.7. Just wondering what the list recommends for a new installation.

Thanks,

• Don