I used a Genie GT-31 GPS logger for a two week bicycle trip through northern England and Scotland. This unit has a SD card slot and is waterproof. I have been using it to log and geotag all my photos (serious ones) for about 6 months now, and I'm only scratching the surface of the 1gig SD card I'm using. The battery lasts almost two days per charge, so it's really a set it and forget it sort of thing. I would get up in the morning unplug it from the USB charger and drop it in my bike bag.
The NEMA messages are written to text files at about one file per 12 hours, so I had 1 or 2 files per day. The files are text files, and can easily be read on the mac with an SD card reader.
I used houdahgeo to geocode (and reverse geocode) about two thousand pictures (in one project). HoudahGeo worked flawlessly, and the GPS accuracy of the SIRFIII based logger was shocking.
I know finding a mac friendly GPS logger can be annoying. I just thought you all might like to hear about one that worked well for me. I have no affiliation with the product. (it was designed for speed wind-surfing competition I think).