I really like my eTrex Vista HCx. On my last tour in 2008 I used Energizer Lithium batteries, and got somewhere between 1 and 2 weeks with the unit on all day while riding (to record trackpoints). I find the disposable Energizer lithiums seem to give much better life than the alkalines. They are more pricey, but also very lightweight. You can easily carry a few spares in one of your bags without even noticing them, and have enough to last for a couple of months.
The eTrex Vista HCx has a bit of a known problem with the glue that attaches the rubber surround coming loose. Fortunately I got my unit from REI and they exchanged for a new unit more than a year after purchase. I think it's caused by leaving the GPS in a hot car in direct sunlight too much, since I had no problems while on tour, but came unstuck after leaving it in the car a few times in the sun.
The 60 CSx is also a very well regarded unit. You want one that takes 2 AA batteries, and has a micro-SD card expansion slot so that you can load up a 2 or 4 GB card with the whole of City Navigator for North America. The big downside of Garmin is the way they do their maps licensing - if you pay $100 or whatever for City Navigator, it is tied to the specific GPS unit that you load it onto. So if you buy a different GPS down the line, you have to buy City Navigator all over again (even though you still have a perfectly good DVD). A bit draconian and annoying, but it's their product, until someone really challenges them in this market they can pretty much do whatever they want. The eTrex does have its quirks (e.g. sometimes some strange routing decisions), but despite these I really love the thing. It's so useful. My main wish is that they could upgrade the POI (Points of Interest) database in City Navigator to have a more comprehensive list of motels and grocery stores, and get rid of the useless knitting supply and timber stores. What traveler needs timber stores anyway? Their choice of entries seems almost random sometimes, including some useless farmer's feed store and leaving out a motel that's been there for 40 years. Does a farmer need the GPS to find his local feed store? No, but your average person using GPS does want to look for lodging, gas, groceries and entertainment (movies etc) when they are on the road.
I would always tour with my GPS now on tour... I know some people sneer at them and think they are a luxury toy, and that's kind of true - but it's a very USEFUL luxury toy which makes my life better... kind of like indexed gearing - do I need it, no, friction works fine, but indexed makes shifting just that bit more convenient. I really appreciate being able to find my way across strange towns without having to buy local maps or getting lost in the "wrong" neighborhood at dusk. The POI database is incomplete, but still useful for finding out what types of services upcoming towns might have. And the trackpoints feature lets you see exactly where you went later on a Google map.
Neil