I've just got the UK TOPO map and am pretty impressed bearing in mind I'll be using it with a paper map
I've loaded all of Devon 3rd largest county in England in the 64Mb
I'm new to GPS but have been mountaineering for years. With good solid navigation skills this bit of kit is awsome.
Take a look at the Garmin website, the Garmin 60 CSx is http://www.garmin.com/products/gpsmap60csx/
If you don't want the compass or altimeter, you can save $50 in the US and go for the http://www.garmin.com/products/gpsmap60cx/ , although I had problems finding one.
UK TOPO works a treat plug in a start point and a finish point and off you go. I 've even been taking wrong turns to see what it will do but the darn thing finds you a new route. It bleeps at you before you need to turn other units have a nice lady to chat to you. I prefer the bleeps.