If it's something you care about... pretty important.
It may not look like there's a lot of difference between the marine products sold at Solid Signal and other products sold for land use. For example, this radio:
probably wouldn't look out of place in a car, at least if you overlooked the white color. Yet, it's designed specifically for marine use. That means it uses the right connectors and the right voltage for marine connections. It's water-resistant (including the speakers) meaning it's going to survive at least casually getting wet. Any component that's out in the open is rated to survive against the highly corrosive salt air. It's just a better device for putting in your boat, which is of course the whole point.
If you care about a piece of electronic gear, it should be marine rated if it lives on your boat. If you use "plain old" electronics, they will fail faster and probably when you need them the most. That's the whole point.
Luckily, almost anything you want to put on your vessel is going to come in some sort of marine rated version. That includes entertainment gear, too -- satellite, TV antenna and cellular booster equipment is all available in marine-optimized packages. If something isn't marine rated and you want to keep it safe, it will have to go deep in the cabin, as waterproof as possible, and protected with a surge protector so that it won't short out if it gets wet.
The fact is, there is a difference, and it's important especially for emergency gear. If you're interested in getting the best marine-rated electronics, check out the selection at Solid Signal now