I would not suggest the GF Spa. it's over priced and they use so-so products anymore. The waiting area is often over crowded so people are left standing (who wants to stand in a crowded room while trying to relax?!), and IMHO it's highly over priced for the quality of services and products they provide.
At Mandara the surroundings are far nicer, the treatment list is much more inclusive. Canyon Ranch is also in the same price range, but the facilities are amazing, and their treatment products are amazing. And they make a ritual out of a manicure like no one else can.
If you've got a car, Canyon Ranch is my first choice.
Another option if you want to take a 35 minute drive up the Greenway is Fawnfeather Spa in Longwood. They are consistently named the best day spa in the area, and their prices are a good 20-30% lower than the Disney area spas.
Canyon Ranch, the WDW Spas, and Mandara all charge in the $120 range for a 50 minute massage. I'm having a 50 minute hot stone massage at FawnFeather tomorrow for the same price. (Thanks to a gift certificate I won in a charity raffle.

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