Summary: I purchased this because my 276C stop working. I purchased a Garmin 620 but you can not see the screen in direct sun light. If your in a cabin with the 620 it would work great. The 376C is easy to use and with the Ram mounts that are available you can mount it about any where. There isn't anything that I dislike about this unit but if there is anything they could do to make it better it would be to enlarge the screen to the 620.
Summary: Very versatile GPS, currently own a 276C that is mounted on my motorcycle, cracked the screen so got the 376C. I use it for road routing mostly but I do like the tide table feature, wife and I go tide pooling along the coast. The 376c/276c are more like a small computer than a GPS, owned a NUVI for a very short time, I ended up taking it back, the features are very limited. Haven't used XM radio but was thinking about getting XM weather.
Summary: I bought this to replace my GPSMap 182c. I was able to take out my bluechart chip, connect it with my GSD 20, and even use the existing wiring in my boat. It was an easy install and the portability is great. Although the screen size of the unit is smaller than the 182c, it makes up for it with a higher resolution screen which enables me to read the fish finder more accurately.
Summary: Having become familiar with Garmin products in aviation, I found the 376C to be extremely easy to use with user friendly menu-driven functions. While not perfect, the unit's database will get you where you want to go everytime...which takes the stress out of city travel. The only glitch, we ran into, was the database's refusal to allow travel northward out of our street (instructing us to proceed southward and then suggesting a U-turn at the next light).
Summary: This is my third Garmin GPS. The other brands are either harder to use or missing features. I love the XM radio and XM Weather. It's very waterproof. I use it on the motorcycle in the driving rain without any problem. My only complaint is you have to use Garmin memory cards for extra maps (lake maps or topo maps or detail down to every house address maps) but the base map included has all the towns and highways, not just the interstates.