i use a Forerunner 405 so I can use it running, riding and occasionally walking. Only really use it for logging data so not worried about having something with a big screen. Also it gives me 6hr battery life which is usually enough for everything but the longest rides. With that in mind I might treat myself to the 310XT at some point as it has 12hr battery and you can swim in it.
As for ease of use, after initial setup, it is as easy as pushing start and stop. This is only my experience of logging, and those who use the GPS for navigation will know more on this side of things.
When you sync your data, for me it is via the Ant+ USB stick, it automatically uploads to the Garmin Connect website, which has really come on in the last year or so and could probably be used just by itself for data analysis. Here is a sample from a recent ride:
http://connect.garmin.com/activity/64596105?
I am on a Mac and use Rubitracks as well. Windows users have Sports Tracks I believe.
Just as a little push after running the iPhone and Garmin side by side to track routes, it is surprising how inaccurate, apparently I am Jesus as I biked across Derwent Reservoir, the iPhone can be sometimes.