I have had the 376c for about 8 months or so now and though I mentioned in my review that I had to return one (dead XM antenna) I have not had any issues with the replacement. I have had several power connectors break on me, but Garmin has so far been good about sending me free replacements.
#2 is called XM WX Satellite Weather and actually downloads the graphic type weather information to your GPS. This service isn't cheap! $30 for a "fisherman/sailor", $50 for "professional mariner", or $99 a month for "ground". And there's an activation fee on top of this. Damn! They're proud of those pixels.
This seems to be a common misconception. The $99 Ground package is NOT available with the 376 or 378. It is a special package for weather chasers and only runs on a PC with special software. The ONLY packages that work with the 376/378 are the MARINE packages, and they run $30 or $50. The $30 package provides everything you really need. You also can deactivate the unit for up to 60 days when you don't need it so you don't have to pay the montly fees without having to pay another $50 activation fee (just don't leave it turned off for more than 60 days). If you have XM radio already, this unit will allow you to put your existing XM radio subscription on the "Family Plan" which will save you another $6 a month on that subscription. Both the 376 and 378 also have built in XM radios.
I can tell you this thing has saved me several times already from riding into a storm. For me, it is worth $30 a month to not ride headlong into a huge storm cell but instead be able to route around it. It has saved me twice already from riding into hail. When I look at the safety and convenience it provides me, the $30 a month fee seems like chicken feed. If you have ever ridden in a storm or heavy rain, you know what I am talking about. If all you do are short day rides and never get more than 100 miles from home, then this unit is probably overkill, but for anyone who rides long distances and crosses many states in unfamiliar territory, it can be a lifesaver, literally.
I believe I posted some photos on the review of the Master Mariner Package as well as the Sailor Package. You can switch from one package to another anytime you want, they just pro-rate your bill.
The 378 does NOT include the XM antenna like the 376 did. They make you pay another $200 or so to get it, and the weather won't work without it, but you don't have to buy the software separate like you did on the 376 so it probably is a wash.
I am taking a 17 day trip from Texas to Maine, and I can tell you I am not sure I would even go if I didn't have the 376 due to all the rain and bad weather they get up there.
I have lots of photos of the 376c posted here. I use it on both the Wing and the FJR.
https://www.pbase.com/fredharmon/garmin376c
Getting the antenna mounted can prove to be a bit of a challenge....