I had to downgrade from Safari 4.0 DP to get clicks to respond. But Mail is working fine - just sent a test one.
Contacts are weird though - they're nothing like the ones on my address book, which I haven't changed since sync. No pictures, barely any contact details. Can't log in through System Prefs to resync either.
EDIT: Ok, the contact details have magically appeared for some people. The contacts page really needs some working on, though (in fact, the whole site's buggy and slow. Getting endless loading loops whenever anything changes). I also think they need more address and phone number formatting options - you can't lump us in to US/FR/DE/JP. It sucks for UK numbers, and sometimes you have international numbers.