FWIW, I am up to 5 Garmin units. I have two that are outdoor styles used for hiking and with a mount for cycling. One is an E-Trex Vista HC, and the other is an E-Trex Vista HCX with the more sensitive receiver. I also have two Nuvi automotive units. The latest was gift from my mom to update my older Nuvi.
When we were purchasing the Spyder, I was fine to not go with the oem GPS setup of 660 and the mount kit. The wife was the one that said she wanted it. So, it arrived in a box, with crappy instructions, but overall was a pretty basic install.
Being familiar with Garmins, the 660 is pretty straight forward and the package works well. It does have Can Am specific items preloaded. I hope it does have lifetime map upgrades or I will be a bit irked, time will tell on that since I have heard various opinions.
So, what was the plan if I did not go 660. I was considering the possibility of using a newer large screen hiking Garmin, obtain the current maps from "Open Street Maps" and contend with loading those maps into the unit. Not normally a super easy task, but not impossible once you understand it. Plus, it gives you maps, anywhere in the world...free, if you can sort it out. (FWIW, luckily I was able to get Open Street Maps loaded for our trip to Ireland last summer. Loaded a Nuvi and an E-Trex with the same map set. Both worked like a champ. Saved my bacon too, since the rental car was reserved with a Garmin, but none were available when we arrived)
I have heard the desert truck racers use Magellans. Supposedly a bit less user friendly, but better performance in harsh conditions. Have not researched it. Just an idea.
Overall, the oem setup does what it should, you get a decent unit and install, Garmin and Bombardier make a profit. One complaint would be direct sunlight. Garmin can say what they want, but it is difficult to see the screen in some lighting conditions. I need to make a glaresheild or buy one. The location is a contributing factor. I almost wish the unit could be panel mounted in a tray, popped out when needed to be stored. Kind of like an AirGizmos tray we use in small airplanes. With the oem display and a Garmin beside it, it would have a two tube EFIS look sort of.
http://www.airgizmos.com/496-Panel-Dock_p_8.html
If you do your own install, one tool you may need to purchase will be the 3/8 drive allen tools. You will need both a 7mm and an 8mm.
PK