The Magellan GC is an excellent unit. Make sure that it is using the latest firmware. It's simple, although it can take a couple minutes, to install the latest firmware.
Magellan does have a software package called Communicator that makes it simple to transfer caches to the Magellan GC and there is a Mac version. However the unit when attached to any computer (Windows, Mac, Linux, etc.) acts as an external hard drive. So the Communicator software isn't necessary unless you want the Sent To GPS feature at geocaching.com to work. But since you are a premium member I wouldn't bother with that. Just generate PQs, download them to your Mac, then copy and paste them to the Geocache directory on the Magellan GC. Logging them is even simpler. The Magellan GC will create a field notes file. All you have to do is upload the field notes file to the geocaching.com website to log your caches!
There are plenty of Magellan GC owners who read these forums so if you have any trouble figuring something out, all you have to do is ask.
THANKS! I appreciate your feedback!