I've had a 60CSx for coming on 3 years and it gets used just about every week. I've told some friends that its such a good unit that I'm considering getting a backup 'just in case'.
You must have Garmin software to use on the unit. I have Garmin's Mapsource 100k which is all the USGS topo maps for the entire 50 states at a 100k resolution. Also have Nat'l Parks East. Thats 24K and has most of the eastern seaboard Nat'l Parks, plus the Greens, Whites, ADKs and BSP.
Although some done do this, most of my fellow 60CSx users also have the Nat'l Geo software. Thats to see reproductions of the full USGS quads on your computer, to draw routes that you upload to your GPS unit. And you can visualize in great detail the tracklog of your hike onto the NG software for review afterward.
The SirfStar chip in the 60CSx was a huge leap forward. In rain, clouds, fog, snow on trees, in deep cols and behinds big trees and rocks, the 60 simply refuses to lose signal.
I will also accept multi Gibabyte memory cards. With a 2 Gb card, I have around 2,000 full USGS topo maps in the unit. Travel out west? Just go to your hard drive where you might have stored other mapsets, and I then just download the topos for the part of the country where I'm travelling and hiking.
After 3 years of intensive use, my perceived drawbacks: The use of lithium batteries is 'iffy' with some units. The unit senses the slightly larger voltage of a new lithium battery and shuts itself down. The Garmin techs have told me that this happens with some users and not others. Their fix is to put the lithiums in a flashlight or other electronic device and run it for a few minutes. A PITA, but it can work. I prefer to use high quality rechargeables, cheaper and easier on the environment, and carry a pair of 'preused' lithiums as a backup.
Also, there is a limt on the number of USGS quads you can download regardless of memory card size. Its somewhere under 2,200. It would be nice if they fixed that(unless they did already and I'm not aware). That would allow you to use a much larger card and put the continenal USA on it.