I like the low profile of the Garmin stock mount more than RAM mounts. You do need to be sure it slides all the way in place when you attach the unit though.
Under track setuo there are various options that influence how often trackpoints are recorded. To get the most accurate tracklog distance, set it to one point per second. Note though that it will archive the track in less than three hours at this setting.
I find the 62s a bit more user friendly, due to more buttons, their layout and button labeling. It's also easier for me to use mountain biking as I can toggle pages pretty well without looking at it.
I second the eTrex 20.
Also, with any GPS, it will take a while for it to lock satellites after travelling a significant distance, so plan to leave it on, under open sky for a full half hour after arriving.
The answer to both is... possibly. I'd check out Magellan's Content Manager: http://support.magellangps.com/support/index.php?_m=downloads&_a=view&parentcategoryid=12&pcid=358&nav=0,358
They use to have a POI manager, but I'm assuming this functionality is part of Content Manager now.
Whether the Bluetooth works with a particular phone is hard to predict. Usually they do though, on Garmin nuvis at leat. Decent voice command may be hard to get in your price range. I find that it works very well on the nuvi 2495/2595, but they are over $200.