I think that most hotels in the "real world" call their equivalent "club level" or something similar. Typically my experience in non-disney hotels is that the concierge desk is their to help any hotel guest, with local information, getting dinner reservations, directions, tickets to shows or sports, and you should tip accordingly. The concierge desk at Disney resorts is different in that if you are staying at the "concierge" level then you have already paid for this service as part of your room, and so gratuities for services like that aren't available. At most hotels in the real world, the concierge will set you up with reservations or tickets for something you want specifically, or will recommend something if you don't know what you want already (this is how they can get the connectiongs to get those hard to get reservations or tickets, they are sending customers to things). I never tried it at wdw, but I suspect that they wouldn't be able to help you get you things outside of wdw (like if you wanted tickets to a ucf game or something off property). The way it is done at wdw is pretty unique in my experience, as are a lot of things I guess.
We've done it, and it is sort of neat, but I'm really not sure if it is worth the extra $ really. It is just as easy to get PS for yourself, because you still have to communicate with someone to tell them what PS you want! Might as well just talk to member services yourself. I think they may note on the PS that you are in concierge, but I don't think it really gets you any notice or anything. If you wanted cinderella's breakfast or something, it might be worth it. I really like being able to grab or coke or water on the way out, but heck, for a couple of bucks you can do that anyway. The food is nice, but then when you are at wdw you always have a lot of meals to go to anyway so you don't want to "waste" one on grazing at the conceirge lounge - but it is nice for a snack. So if it is an extra 25 or whatever a night, is it really worth it? It is up to each person, I'd probably do it again if we didn't have dvc, and we might anyway for a weekend or something. The polly has a pretty neat lounge, and the AKL has a reason to stay concierge - the early morning safari that only conceirge guests can go on.