I've got a Garmin 305 that I've been using year 'round. It works well for me in all kinds of conditions, including in dense forest on cloud covered rainy days.

It's exactly what I need for several reasons, not the least of which being that my local riding area is very large, and made up almoste entirely of unmarked trails that appear and disappear over time. There are no maps (except for a couple of bootleg maps created by friends of friends). I'd love to get the 705 so that I could load up topo maps of the area too, but that's a pretty penny and I can't afford it for just now.