Pros
Free drinks, half-off food. If you have good coworkers and a decent manager, it'll be nice to talk to someone while you wipe the windows. It's also nice to know the "ins and outs" of the restaurant and know things that most people don't. I've sometimes received tips. There are also a lot of customers coming through, so you get to interact with many people. Some of them are even good looking.
Cons
It can get dirty. If your managers are mean, that's tough to endure. Also, your coworkers could be jerks. And the customer is always right, even when they're not. There have been many times when I've had to explain to my (angry) mangers that I did everything correctly and that it was the customer's fault. Customers can also be rude and condescending. I bet the environment doesn't do much for your pores either, though I saw no significant difference.