I'm another Zumo 660 user.
Good Points:
- weather proof for bikes
- regular updated maps (which come lifetime free at purchase)
- bluetooth comms system if you want
- integrates into comms system without hiccups (eg Starcom1 & Autocom etc)
- Ram Mounts included with purchase
- good brand so plenty of support (including a Zumo Forum hosted by Garmin)
- easy to use and generally pretty intuitive in controls
- plenty of accessories and replacement parts available because its a common unit
- can be wired direct to bike for power supply in cradle provided in box
Bad Points:
- not cheap start up
- some known minor issues (easily fixed)
- can be difficult to read screen in bright sunlight
I know some people will think of more points to add to the bad, however mine has now done around 90 000km since new in Aug 2010 and still going strong. I have a cradle on the ST11 home bike & FJR13 work bike that the unit swaps between. Used to find addresses in a hurry at work, spends days on the road for home, and I ride in rain, hail or NQ hot weather, so it doesn't get babied. Bought an anti-glare screen protector for it, and generally don't have to many issues.
The other two riders in our office have been supplied the Strike GPS, because I provided my own, and one doesn't use it, and the other says his is only good for playing music into his helmet. Neither of them have a great deal of experience with GPS' so whether that would make a difference I don't know, but for now I am more than happy to recommend the Zumo 660 as a capable device. There is a new model out now, but you can still get the 660.