I've been through the same thought process as you, and I bought the Garmin eTrex Vista HCx last year, mainly for the POI (points of interest) database - gas stations, motels etc. Here are my thoughts:
1. The HCx line is much more sensitive than the earlier models. While sometimes my eTrex would lose track next to large bluffs on the KATY trail, it was mostly rock solid in terms of keeping a signal. It can even pick up the satellites in my house. The newer receivers really are a jump in quality from earlier models.
2. The big differences between the eTrex and the 60CSx are as follows: First of all, the 60CSx has a better, external helix antenna (you also have the ability to attach external antennae if even more sensitivity is required). The eTrex has an internal antenna, and no ability for external. So the 60CSx has the edge in picking up and keeping a signal. Second, the screen on the 60CSx is a bit bigger. I don't know if the resolution is any different. Third, the 60CSx is quite a bit bigger than the eTrex - it's longer, and the antenna sticks out more. This can make it harder to mount on your handlebars, especially if you have a handlebar bag. My impression was that the 60CSx is more for hand-held use (it looks like a walkie talkie) and it also has the buttons all on the front, which is much more ergonomic than the eTrex. The eTrex has a little joystick on the front, mysteriously placed above the screen so that your hand is always over the screen when manipulating it. Weird design. HOWEVER... for bicycle use, I'd probably still go for the eTrex (though I really like the 60CSx), mainly because of the smaller size. Otherwise, they are probably largely identical in terms of software - they both have expandable SD card slot (that's the 'x' in the model) and color screen (the 'C') and I'm not sure what the 'S' stands for, but it's probably something to do with 'sensitive', since that's it's speciality with the helix antenna.
3. The eTrex screen is tough as nails. Literally. The only scratch I have on mine is from a nail board I accidentally left next to it in the handlebar bag one night. Otherwise, it's spotless. I think they made it of some super-tough material, which is very nice. I wouldn't like the new touch-screens as much, frankly, because they are softer and I don't want to be always smudging the screen with my fingers. However we might get one of the touch-screen Nuvi units for the car eventually - they are actually quite nice.
4. The Garmin City Navigator software allows you to load the entire street-level maps for North America (including Canada) onto a 2GB mini-SD card. This includes the POI database. However, in practice, this database is not to be counted on, especially in the middle of nowhere. There were many instances on my trip last summer where I looked for motels and grocery stores in little towns, and it came up blank. So I would then call my wife at home, she would use Google, and find stuff. Obviously they didn't (couldn't) include a full yellow pages for the entire country; not even close. What's frustrating is looking at what they chose to include - weird stores like knitting supplies or lumber, which have little or nothing to do with what travelers will generally be interested in. Sometimes the selection seems totally random. I wish they would cull the database of useless entries, and focus on those things that travelers need - lodging, grocery stores, gas stations etc. Having said all that, the POI database is often very useful, but more so in the larger towns. You can usually just find a Super 8 or whatever, and be routed directly to it. Don't get me wrong - it does work, it's just not complete by any stretch.
5. Routing: I never made my own routes on the unit; I just put it into 'bicycle' mode (in the setup) so that it wouldn't try to take me on highways. I usually had a rough idea of where I wanted to go, so what I would do usually is find the next small town and say "take me there", and it would do the job admirably most of the time - often on the same route that I had pre-planned on my map. The only times it didn't do a stellar job in the routing is when it came to differentiating between dirt roads and highways. Sometimes I would be going along a very nice road in the middle of nowhere, which the GPS thought was some kind of highway, and it would keep trying to get me off this nice road onto little dirt tracks. That was occasional, and actually quite amusing (because you can simply look ahead on the route to see where it wants to take you, and decline the turn - it recalculates the route almost immediately when you decline a turn, which is GREAT). I love the routing on the eTrex HCx. We also use the unit all the time in the car, and it has become our best friend on the road - any new town in the country, we are never, ever lost now. It's quite amazing. It doesn't talk to us (as the newer Nuvi car units do) but the little beeps are very audible and quite fine for me.
6. Cost: I'm not thrilled with Garmin's policy of locking City Navigator to one single GPS unit. You have to register the software with that particular unit. If you get another unit, you have to buy City Navigator all over again, which seems a little restrictive somehow, but it's their call. Garmin currently make the best GPS on the market, so they get to call the shots. HOWEVER: One of the big attractions of the DeLorme PN-40 (which I've looked at recently) is the ability to get a subscription to their maps for just $30 per year (VERY reasonable, Garmin take note that I'd be more than happy to pay that every year) for all-you-can-eat downloads of any and all of their maps, including topo and satellite imagery! One of the great things about the PN-40 is it can display Google-Earth-like image overlays, which is mind blowing. However I asked about comparing the PN-40 to the Garmin GPS on the DeLorme forums, and the overall impression I got was that the Garmins still have a slight edge - but look out for DeLorme, because they seem to be improving in leaps and bounds. The main deal breaker for me was the battery life - the PN40 only gets a few hours, whereas the eTrex can last a lot longer (a week or two with the Energizer lithiums, which are HIGHLY recommended - they are expensive, but they ROCK - lighter than alkalines, and really worth it for the road). Here's the thread:
http://forum.delorme.com/viewtopic.php?t=17118
Overall, I'm extremely happy with the eTrex Vista HCx. I used to have a Magellan SporTrak from 2003 or so, and it was frankly awful - slow to grab satellites, inaccurate (it would show us traveling about 50 feet off the road, consistently, with no way to correct it), the memory was pitiful (16MB), and the screen was mono. But the newer units really have advanced to the point where they are actually really useful, not toys any more. Color screens, fast processors, sensitive receivers, expandability, you can just load up the entire country in one go, the POI databases (which will hopefully get better over time), the routing... these things rock. If you get one, you'll fall in love, even with all the little quirks and flaws. They are that good, you just find yourself forgiving stuff all over the place.
One of the best gadgets I have purchased in recent years!
Neil