I do weeks at both Saddlebrook and Newks on a regular basis for years.....love both. Since I live about 2 1/2 hrs from Newks and my youngest is at the academy there I am partial to Newks. Really no matter which adult program you choose you will get solid tennis - Newks tries to have a laid back "Aussie" style with solid workouts but lots of bar time in the evening - hahaha and on many weekends you can get some really solid players the accommodations are nice but for sure not 4star. Saddlebrook sells itself a bit more upscale and the tennis workshops can be brutal (I remember a bootcamp workout a few yrs ago on the 2nd day and I could barely walk back to my condo).
The Academy at Club Med at Sandpiper (near Port St Lucie, FL) is also good as long as you do the Academy Program - I like it as well but it is pretty expensive As you have to pay an extra fee for the Academy intensive total tennis - of course all the extras you get with the Club Med package is great - only negative is the location as it really does not have a beach (it's on the intercoastal) and they have a baby club (some weeks it seems that's all you see are lots and lots and lots of kids).