Al, for your use I think it's important to get one of the newer Garmin units that accepts 500 raster map tiles. I *assume* the GPSMap 64 series can do this, but not 100% sure, so you should do a little research. Otherwise, I'd say that the GPSMap 62 series is more attractively priced, but I know it can only accept 100 map tiles. The 64 series also has GLONASS, which might provide more accuracy (have not seen any definitive proof though), but should definitely help with quick satellite acquisition and challenging signal conditions. Basically, it means that the GPS can lock onto additional satellites that older devices don't see.
Unfortunately Garmin does not make any button-based devices with high resolution screen. The GPSMap and eTrex series all have very low res screens. You really might want to spend some time at a store like REI and play with the Montana 600 however. It has the nicest screen - 4 inches at 272x480 pixels. It's a touchscreen, but I don't have the kind of problems you describe. You can lock the screen to prevent accidental button pushes. The touchscreen really makes it easier to enter text and numbers - if you rotate the screen to landscape view, you get a standard QWERTY keyboard.
I also have a Triton 1500, and the user interface is terrible on these. I would not compare them to Garmin in any way. There are plenty of things to nitpick about with Garmin, but they are way ahead of the Triton in usability. The Oregon 600 series is also worth a look if you want something smaller. I think Guy said that Bob got one of these?
G-raster should be a good program, the author is a cool guy and often helps people over at GPSFileDepot, and he actually runs the FreeGeographyTools website. I suggest that you also look at mapc2mapc:
http://www.the-thorns.org.uk/mapping/
It allows you to make irregularly shaped maps. The other software only makes rectangular maps, and this often means you are wasting precious tiles with areas that don't interest you.
You could also look at mobile atlas creator:
http://mobac.sourceforge.net
I have not used this or g-raster because Globalmapper does pretty much everything I need. But I have played around with mapc2mapc and thought it was cool.