Pros
Garmin makes a lot of interesting consumer products. Benefits are pretty good. They are a large company in a variety of markets so there are a lot of opportunities for internal transfers.
Cons
Garmin lacks vision and focus. Garmin doesn't know what product to build so they build a lot of similar products which is inefficient and time consuming from an engineering perspective and confusing as hell from a customer perspective. Garmin is a hardware company and they are probably a pretty good place to work if you are a hardware engineer or you like doing embedded software on a proprietary platform. Garmin doesn't understand how to manage modern software platforms like web and mobile so if you work in those areas you will feel like the tail is wagging the dog. In other words the hardware products that Garmin sells generates all the revenue and so web and mobile teams have to do whatever the product teams want even if that means committing software suicide.