Pros
You're selling a happy product that people really like and customers have a lot of nostalgia and fondness for See's (in areas where they have a strong presence, like CA). In the non-holiday periods, you have a lot of regular customers that you get to know. See's also empowers employees to help any way possible to give great customer service. Shops tend to have small staffs (about 5 or 6 regulars) so you get to know the people you work with. In CA they are union, so it's a pretty good pay scale with excellent benefits--I don't know what it's like in other states.
Cons
Like most retail, the holidays suck, and after being there 3 years, it pretty much ruined X-mas for me. Not crazy about the uniforms. If you start in a shop, manager seems to be as high as you can go--there's an unspoken policy of not promoting beyond that--managers don't become division managers, etc. And oddly, some of the division managers aren't very well trained, but you only see them 5 or 6 times a year anyway.