I am looking at getting it for out of province rides. Easier than using the piece of paper on the tank and having to stop and keep switching sheets.
I have paper maps and have generally stayed away from GPS devices ever since I started riding. I used paper maps for my 10 state trip last year and it was serious pain. I had 6 paper maps and 10 laminated ones with detailed routes and good roads marked out. Especially frustrating was moving at speed and trying to figure out my location on the map or if I had missed an exit and so on, or like you mentioned, realizing that I had to switch sheets or change to the next state map. Then it got worse when I started exploring backroads and none of them were on my maps and I was relying on the position of the sun to direct me on cloudy days...
My next multi day trip I used paper maps with GPS and it was awesome. Being able to see the big picture with the paper maps plus having the advanced functionality of the GPS when I needed it made the trip seamless... I will never use just paper maps again - that's just stubborn talking. It took me a few rides to get the hang of it, but once I did, I realize that it is a really great addition to the trip experience. I especially like being able to just go off course for a while to explore an area and than anytime I need to get back on course I just pick my point on the GPS and it's send me there -which in itself often leads to riding on some awesome roads.
I'm using the Nuvi550 based on the recommendations of a few people here and it does the trick.
Price: $200 all in (mounts, cables, taxes shipping)
Pro's:
Waterproof
Very reliable and withstands heavy vibrations
Easy enough to read the screen in brighter sunlight
Easy to upload routes from computer to GPS
Can be used for riding, biking or hiking.
Long enough battery life - around 5-8hrs and quick to recharge.
Con's (for me):
Would prefer a bigger screen like some of the other nuvi's
no mp3
no fm transmitter
no bluetooth