Just to tell how it's been, I've had a few thousand miles with the 276c now.
It's been dusted in big bend, rained on for a couple of pie runs, through at least 4 drops of the bike one of which being a high side in sand dunes, and run in snow and ice with my front tire covering it in mud. The $30 RAM mount from Cycoactive has done well, I haven't even mounted the pricey vibe isolating touratech mount yet.
It's been mounted on my dirt bike through gnarly single track in rain and snow and rocky bouncy climbs and vibrations only a KTM thumper can deliver. It's cooked in my truck in the 98 degree sun.
It'll also go pretty much all day on a battery charge.
It's done very well. The only issue I've had was the desert dust got into the battery pack contacts and made it shut off once, one wipe with a t-shirt and that was fixed.
The 256mb card will fit all of Texas in both street and topo maps and then some, I think 2 of them will be all I'll ever need.
The screen is great, better visibility in direct sunlight than shaded IMO, and the automatic black background night screen rocks.
The options for routing are good, but the algorithms can get a bit weird on where they tell you to go if you go nuts with it. The number of settings for detail and zoom and text labels on roads/cities/rivers/elevation and other settings are impressive and let you set it up to your style, even has older datums, tides, fishing forecaster etc. built in.
The only other problem I have is wiping the screen in rain or mud or snow with dirty gloves, I've already noticed some fine scratches, it really needs some of that palm computer screen protection film.
Overall it's better than I had expected in all details, with the proprietary memory stick limitation being the only downside. It's still the best unit going IMO for now anyway.