I have been using Missing Sync. Not bad. Some report data loss issues, but my installation has been rock solid. I have it on my MacPro and my Macbook. I keep all three synced by Bluetooth.
Sparkly has a MacBookPro and an iMac. Missing Sync works fine on her MacBookPro but has never worked well (at all) on her iMac.
My Blackberry Storm developed some issues recently. This led to Verizon sending me a replacement. I asked about how to transfer all my data. The Verizon woman told me to install their brand new Blackberry Desktop ***For Mac***!!!!
It works great. It has a standard Mac look. It syncs to all my Mac programs - Mail (for notes and tasks), Address Book, iCal, etc. It also does Entourage if that's your thing.
The only downside ...... no bluetooth ...... yet. They say it will be here in an update or two.
I am using it on my MacPro, where I have a dock. I am using Missing Sync with my MacBook via bluetooth. Missing Sync and Blackberry Desktop happily coexist - but only if you set up your Blackberry to sync with more than one computer when you install the Desktop. Installing Blackberry Desktop disables any other syncing program, but only on that computer. The Blackberry device itself works fine with more than one sync program.
http://na.blackberry.com/eng/services/desktop/desktop_mac.jsp