I bought a M125 used off ebay and have been using it with cachemate. I've got over 700 caches stored on it now, it takes up just over 2MB of the M125 8MB memory. The M125 has SD card capacity as well so I figure I've got plenty of space for the future.
My method of transfering files is a little convoluted due to my home computer being a Mac, I use GSAK on my computer at work and e-mail myself the files to install at home.
I've been quite happy with cachemate and the palm, happy to (mostly) get rid of the printed cache sheets. The mostly comes from the trouble I had over Christmas where I went to a new cache with my bro-in-law in the next province over. I downloaded the caches to the palm before I left on my trip and the cache in question was approved the day after I left. We ended up having to go to his office to print out the cache sheet.