"Magellan has a GPS forthcoming that will upload NG Topo! maps. Garmin doesn't have this capability."

Hmm, does it really not work on any Garmin unit? Maybe not, dunno.
If you have a PDA (or smartphone) running either Palm or PocketPC, there's a product called PocketTopo that basically unlocks functionality that already exists in the National Geographic Topo software to do what you want. Works fine on my PocketPC smartphone.

The smartphone is a possibility you might consider if you're into weight saving (combine multiple devices into one). Just be sure to look for one that has the SiRF Star III chipset. Definitely not the cheapest route to go, but if you look round at some point and find that you're separately carrying some or all of a phone, GPS, camera, MP3 player, voice recorder, and maybe a paperback book (plus maybe spare batteries for some of that stuff), then it gets interesting to try to combine some or all of those into a single device.