We have stayed at the Yacht Club in the club level rooms many times. Our experience has been pretty identical to what was noted above. Instead of a separate building, you have a dedicated floor that can only be accessed by a club level KTTW card. We also always use Magic Express and every time there has been someone to greet us when we stepped of the bus and they whisked us up to the concierge floor to check in. It's is a nice perk, especially if there are a large number of families getting off the bus and checking in at the same time.
For us, we enjoy it because of it's so quick and easy to just step down the hall and grab breakfast before heading to the parks. We also make great use of the appetizers in the evening. We always make late dinner reservations - 8 or 9 pm, preferring to tour the parks and ride the rides during the normal dinner rush times, so grabbing a few snacks around 5 or so is a nice way to fuel up the teenager until dinner time. We don't make too much use of the alcohol as we are usually heading back to the parks, but love the option of grabbing pop, etc. throughout the day.
I will add, though, that we only go to WDW when we get a discount on the room rate. The rack rates have gotten ridiculous, and I simply can't justify the cost.