Hello,
I completed the training at ATP a few months back and completed my Comm-ME and the "Total CFI" program. Overall I was very pleased with the program, facilities, aircraft and in most cases the personnel. Like everything ATP has it's good points and it's bad points. I will try and elaborate for you:
1. The Programs: The Commercial ME course will only take you 3-4 days and you'll fly 4-5 training hops and then the checkride. If you study the handout that they send you in the mail and know it cold before you arrive the oral is a piece of cake. You are expected to follow the checklists to the letter and have solid instrument skills/procedures. ATP is set-up like a quasi-military/airline training environment and their are required call-outs and procedures that are well over and above what the typical GA pilot-type is accustomed to. It's all good though

2. Facilities: TOP-NOTCH, building was new and in particular the maintenance side of the house was very well organized, clean and professional. The training side was also clean and well maintained, even if it was a little messy.
3. Aircraft: In general I would say that the aircraft are very well maintained and even though I did encounter a couple of minor maintenance issues. All descrepencies are quickly corrected, and they excel at maintenace admin! Very good record-keeping and if you don't know a lot about maint. admin, you will when you leave there! All the airplanes have Garmin 430s/HSIs and a couple had slaved gyros. I only flew the older aircraft and you probably will too if you are enrolling in the CFI course(s).
4. Personnel: Most people there are friendly and professional, however, because ATP has no admin folks on site. Instructors often will be pulled 4 different directions while you are working with them. That was the only thing that royally p*ssed me off. After all you are forking over big $$$ and the phone ringing incessently or helping other students in the middle of a ground brief is pretty annoying. I'm of the mind that once I'm in my "flight box" I will not be distracted from the mission or it's preparation. This is probably a function of my military background.
Another issue with the instructors is that they KNOW the Seminole backwards and fowards...This is a good thing, however, for the most part are otherwise inexperienced. So, you are not going to "learn" anything new about flying on the whole, BUT in fairness you will be well-trained in the Seminole and ATP's procedures.
5. Miscellaneous: Keep the phrase, "Semper Gumby" in mind (always flexible as a Marine aviator once told me). On just about every day things will not go as scheduled, BUT you will get your hop out sometime during the day. Not a big deal, and you can use the time constructively or take a lot of catnaps

You might feel like you are sometimes being jerked around, but I don't think it's intentional. The instructors are at the mercy of their own internal operations/dispatch system which I thought left a little to be desired from the communications standpoint.
6. CFI stuff: Be ready to study a lot and drink from a firehose. The checkrides aren't too bad. Although, the CFII in the Seminole was a bear for me because I had to shoot two partial panel approaches to a strange airport and one was single-engine! You will feel like a one-legged man in an ass-kickin' contest sometimes while you are doing the instrument stuff at first from the right seat, but it's also a lot of fun too. Did I say that? Seriously, I felt extremely sharp and confident in my abilities as an instrument pilot after I was complete. Keep in mind you'll have a HUGE advantage coming from the Comm add-on course and all the maneuvers will be cake from the right seat. Steep turns kicked my ass until one day something just clicked and they were perfect right before/during my checkride. Seminole is a nose heavy little bugger. Best of luck! Drop me a line via PM for any questions that you may have.
regards,
Ex-Navy rotorhead