Looks like TomTom 5 software and maps. Probably a bit dated, but TomTom software is excellent. Great POI's and mapping. At this price, it looks to be a great deal.
As the previous poster mentioned, you will not have to use data. In fact, I would at times turn off my wireless service as to not interfere with the mapping. The Treo 650 can only manage one Bluetooth device, so you'd need to use a wired headset if you're using the Bluetooth GPS receiver.
Here's a
review of TomTom Navigator which uses the same software as the unit you are considering.
-Chris