I went for the 910xt, as I like to swim out on the coast too.
I run a lot more than ride now, so the 610 might have been a better bet, but the 910 gives me plenty of options.
I don't bother with the course/mapping option, it's too slow to redraw, and I usually know where I'm going ... but even if I don't I'll work it out on the ground, and from reading around online I gather it's pretty buggy anyway.
I very nearly bought the Ambit, but the slew of training data and on-the-fly set up of the 910xt (vs. the need to be programmed via a workstation on the Ambit) won out this time - I can see an Ambit in my future tho' :wink:. The Fenix still seems to be a product in beta, so I'll give that a miss until it's at version 2.
Dunno about Strava, as I don't use it. Garmin Connect works well for me, and of course, the 910 integrates perfectly. It produces GPX files, so it should port over ok, if not something like GPSBabel might help with the translation.
Works fine on the bike, I'm only a slow ole' tourist these days, so I don't ride to 'train', although the 910 was designed with that in mind of course. I really only use it as a data-logger, so I wear it riding too, rather than fit it on the bars.
When the time comes for a mapping GPSr, it'll be a GpsMap 62STC I think (or whatever that becomes) - but that's a whole other discussion.