The touch screen aversion is primarily due to clumsiness of operations with mittens, and cold weather operation in general. It's also another thing to go wrong and if you have a GPS you will occasionally drop it and scratching or smacking touch screens does not make them happy. And with the non-touchscreen versions you eventually get familiar enough with the buttons to work them without even having to look at the screen. But there are some (deranged) people who really love touch screens, so some of it may be personal preference.
Garmin Basecamp and Mapsource are both pieces of free software used to transfer maps, tracks, waypoints and other data between computers and Garmin GPS units. They both give the user rudimentary drawing, measurement and analysis tools. These two programs are primarily the interface between your PC and your GPS. They essentially both serve the same function with Basecamp being a newer iteration and intended to replace Mapsource. I've used both and can comment a bit on them.
Mapsource is Garmin's original interface software and it looks like something Microsoftish from the 1990s. It's always been my impression that Garmin was an excellent hardware company but pretty clueless when it comes to software, and Mapsource contributed greatly to that perception.
Basecamp is much newer and supposedly "better". But it is, after all, Garmin, so execution of many things is unexpected and wacky. It does look prettier than Mapsource. That said, after trying Basecamp I went back to Mapsource as my main Garmin software as it's much simpler and doesn't annoy me as much. It allows me to do what I need to with minimum of drama. If I want to do more sophisticated stuff, I can bring my GPS data into Google Earth or a very capable paid GPS program called GPS Expert.
As mentioned both Basecamp and Mapsource are free and can be found on the Internet for downloading. Basecamp also is included on DVDs when you buy Garmin topo maps (I don't think they still include Mapsource).
Since I'm spouting on GPS software, one other program of note is called GPSBabel. It's freeware/shareware and allows users to change GPS data into most any format imaginable. This allows you to do stuff in Google Earth, convert it to a Garmin format then load it on to your GPS. (Google Earth can open Garmin files directly).
Because Garmin has annoyed many people with their closed source, proprietary maps, there has been a lot of work done on open source maps for Garmins. A major repository for these efforts is
GPSFileDepot. They do have free topo maps of California there as well as tutorials for putting them on your Garmin. It's a bit more work than using Garmin's maps, so me being lazy, I just go with Garmin's. But if you really wanted decent, budget (as in "free") maps, it's a great source. I do recall one tutorial on how to load Garmin's topo maps onto a Garmin Nuvi, (one of their automobile GPS units), which is great for 4WD use as Nuvis have very big screens.
Oh yeah, trackback. Unless there's a very low end model I don't know about, I think they all have some sort of trackback function. At its simplest, the GPS will leave a trace on the screen of your path up to that point so you can just turn around and follow it back. I've done that on a number of occasions when I know my path in has been on a trail and I'm looking to rejoin it on the way out.