I think that Sorcerer's post pretty much covers it, but since you asked specifically about the hotel/theme park benefit, I will add that, yes we get discounts, but they won't do you any good as a seasonal since the "rule" is that all CM's can't request time off from Nov 1 until Jan 15, which is also the tenure of casuals/seasonals. If you have a party to go to and stuff like that, scheduling can be worked out, and it usually is without a problem. That is in part why we hire casusals, so don't flip out thinking that you will be devoting your whole life to Disney, altho it will feel that way sometimes. But none of us can have a few days off to go to WDW during the Christmas season. It is part of the price we pay to be part of the magic.
On a lighter note, there is no better place to be at Christmas then around people who love Disney. It helps to make up for the Grumpies that come in wondering why we don't have Halloween costumes at Christmas.