which Mac OS X client to use with kolab2

[Stefan Armbruster]

Hi,

I'm just getting started with Kolab 2. Which is the recommended client 
application to use on Mac OS X? 
In the archive there's a discussion from June 2005, so things might have 
changed since that. 

What I've found so far:
1) Athera (http://www.thekompany.com/projects/aethera/index.php3) 
Does it support Kolab2 or Kolab1? Since the last release is from early 2005, 
is this project still alive?
2) KDEPIM via Fink
Any experiences regargding installation issues?
3) Thunderbird together with Synckolab 
(http://www.gargan.org/extensions/synckolab.html)
Seems to be in rather experimental state. Suitable for production use?
4) Horde Webclient

Any other options? Which one is preferable regarding "easy-to-use"?

TIA,
Stefan