I use iMate Jam and I think it is great for my usage. The size is just perfect.
Right now as Tiger user I am eagerly waiting for Missing Sync newest version to come out. I never have good experience with PocketMac and won't touch that anymore. But this is just my experience.
Because of that, my Jam does not sync with my Mac at this moment. But inputing data directly to the Jam is not that bad. As long as you are not typing a research paper with the on-screen keyboard I think you should be fine NOT using Mac to input data.
Before upgrading to Tiger, using Missing Sync with Panther 10.3.9 via BT is fine.
There are discussion in many cellphone forums about using Wifi card with Jam with success. I personally don't have one so cannot comment. But at the end it is just a PPC so as long as that hardware is compatible, it should work with Jam.
Search for PPC discussion board and you get lots of helpful info.