[QUOTE=ianzin]
Cinehead wrote “Are you travelling with kids?” and Ruby wrote “If you’re travelling with children”, so I guess the final line in my OP just wasn’t clear enough: No children. Just myself and a friend hanging around and seeing what it’s all about.
[/QUOTE]
Ah - if just two of you, you’ll be comfortable at any of the Disney resorts. When we went last year, we were considering taking a friend’s 13 year old along with our two, and for 5 people, the onsite options are very limited and/or expensive. The rooms and pools improve with the levels of resort - the budget resorts are motel-cheap and have basic pools and limited onsite dining; the moderate resorts have nicer pools and better onsite dining, and the rooms are slightly better (I think; I’ve only stayed in a moderate resort). The deluxe resorts can be fantastic - I’ve dined at the Polynesian and at Animal Kingdom Lodge and the grounds and indoor public areas are stunning. However you pay lots of $$ for that. Think about how much time you might spend actually taking advantage of the hotel facilities when you’re deciding where to say. When we went last summer, we swam perhaps twice and ate at the hotel perhaps once; we did use the bus transportation every day.
Depending on what time of year you go, you can get decent rates even on-site. What time of year are you thinking of going? We went in October 1987 (this was pre-kids) and lines were pretty much nonexistent, and hotel rates (we stayed in Kissimee, just a couple miles away) were the cheapest of the year. You’ll want to avoid the Spring Break period (late March / early April) if you can as it’s likely to be crowded. Also high summer is unpleasant… somehow we always wind up going there in July though.
The Disney Dining Plan can be a good deal for adults. It’s 40ish dollars a day which gets you a sit-down meal, a table-service meal, and a snack. We did that last summer and though the kids didn’t typically eat much of the bigger meal, some of the table-service meals would have been pricey enough that this paid for the entire day (we had one at Kona, I think, that would have been 180 dollars). This is only available if you stay on-site though.
I do recommend the Unofficial Guide to Walt Disney World. It has scads of information on all the parks, including touring plans that help you avoid the worst of the lines and maximize your riding time. We didn’t do the touring plans - we wanted to play it by ear - but the rest of the book was invaluable. And one of the authors is a Doper 
Typo Knig and I are planning on going again in October 2015. Why plan so far in advance, you say? Well, our youngest child will be in college that fall. So we can enjoy the short lines and cheap rates and not have to deal with the WHINING and we can ride what we want!
Definitely do the Magic Kingdom and Epcot. This, surprisingly, was a huge hit with my kids last year - we actually spent 2 full days there. Disney-MGM was so-so, in my opinion, though as the Unofficial Guide says, the Phantasmics (I think that’s the name) show in the evening was really worth it. If we were doing it again, we’d probably skip MGM altogether, except perhaps for the show. Then again, the only really interesting “rides” there were a bit too scary for my kids.
Animal Kingdom is worth a visit but if time is tight or you’re really enjoying Magic Kingdom or Epcot, you can miss it.
I haven’t visited either of the waterparks but they’re supposed to be very good.
There are other parks in the area, which are not Disney-affiliated. Sea World is worth a visit (though getting there might be tricky if you’re staying on-site at Disney and don’t have a car). Ditto Gatorland which is worth a couple of hours if you have half a day to kill - when we went 5 years ago, we arrived early in the morning on the auto train, didn’t want to hit a Disney park, and that was just right for an afternoon’s diversion. That’s also not Disney-affiliated. And Universal Studios is, I imagine, someone similar to Disney/MGM; I have not visited it.
Discounts on onsite hotels and theme park tickets are hard to come by. Some travel agents can save you a little; we went via AAA (American Auto Association) and saved perhaps 250 dollars for the week, for 4 of us. I couldn’t find a better deal anywhere.