Check out the Garmin Montana. It's got a noticeably brighter screen, and very customizable. If you don't need XM radio or weather or an MP3 player, but just a good GPS, its a winner. Easy to customize too. This is the favorite of the ADVider crowd.
I'll add another vote for the Garmin Montana. I bought one a couple of months ago and have been very happy with it so far. It replaced a Garmin Quest 2 that I've been using since 2006. The flip-up antenna connection on the Quest had worn out, so the unit was having a tough time receiving the GPS signals. When it did receive the signals, the processor was so old and slow that it just couldn't keep up anymore. The screen refresh rate was incredibly slow. Once I programmed a route on the Quest (very easy to do, btw), it would take several minutes to calculate a solution. It was time for a new GPS.
I don't like the Garmin 550/660/665 series. They are way more GPS than I need. I don't need XM radio, weather, bluetooth, or an MP3 player. I just want it to be able to navigate. Plus, I have 2 buddies that have had the 550 and 665. From my limited experience with them, they suck. They've been very unreliable, needing multiple replacements from Garmin. The screens aren't that great in bright sunlight. I rarely use MapSource/BaseCamp to program routes...while out on a ride, I always program routes on the GPS itself. On the 550/665, programming the route is a real pain in the arse. Clunky user interface, way too many steps required to add waypoints for a route. The responsiveness of the touchscreens just blows...very difficult to scroll around the screen. Maybe they both have bad digitizers? Also, they have extremely limited battery life. I swap my GPS between three bikes, and I really don't want the hassle of hard-wiring GPS power on all three machines (I'll admit that I'm really lazy). I need long battery life.
All of those factors turned my attention to the Montana. I read the huge thread on ADVrider and placed an order for one. I got the base unit, the 600. The 650 comes with a 5MP camera, which I have no use for. It only comes loaded with a basemap, so I also ordered City Navigator North America mapset. Not a dealbreaker for me. The thing is huge compared to my old Quest. Huge screen compared to the Quest as well. It seems to be very rugged. The unit can be mounted with the screen in portrait or landscape mode. I thought I'd prefer portrait mode, but I actually keep it in landscape mode all the time. The screen is quite bright, very easy to see in bright sunlight. In dimmer lighting conditions, the backlight makes the screen easily readable. I keep the backlighting as dim as possible (or off) to conserve battery power, however. Battery power is another neat feature of the Montana. When you open the battery hatch, you can see 2 power options. It comes with a rechargable lithium-ion battery pack, which should be good for up to 16 hours. If you run that battery dead for some reason and can't recharge it, you remove it and put 3 AA batteries in the same compartment. The AAs should last up to 22 hours. Last week I rode from Palm Springs to Durango CO, 687 miles in about 11 hours...the li-ion battery was down to 30% when I rolled into Durango. Nice. I don't have to hard-wire anything. Did I mention that I was lazy?
The Montana is also really easy to use. The touch-screen is very responsive...works great for scrolling around the map with gloves on. Programming a route on the unit is SO EASY. Way easier than the 550/665. Plus, as Hudson mentioned, the screens are very easily customized. The icons can be moved around wherever you want them. The commonly used ones I moved right to the top. The never-used icons (geocaching, hunt & fish, area calculation, etc) were moved way to the bottom pages. Very cool. I never thought I'd say that about a Garmin GPS.
Here's a page with some useful info:
Garmin Montana Wiki
It's a neat GPS. I only have about 4000 miles with it, but so far I really like it. Sorry for the long-winded post!