I have applied to all four for the 2011 classes. I applied to NAU alone last year and got an interview but wasn't offered admission to the 2010 class so I expanded my target schools this time around. Franklin Pierce has contacted me to schedule an interview and the other schools have also been in touch (we received your application, etc.).
NAU is obviously my first choice due to the lower tuition (I live in AZ) and the fact it's a highly rated program. After my visit with them earlier this year, I'm even more convinced that it's the best choice for me. Since I haven't had any conversations, interviews or tours of the other three, I can't really offer any first-hand insights. I do have to say I am a bit concerned about Franklin Pierce since they backed out of their arrangement with the City of Goodyear to build a permanent campus there. Both AT Still (ASHS) and Midwestern have permanent facilities in the Phoenix metro area. Also, I know Midwestern is not yet CAPTE accredited but I'm really bothered by that because their Illinois program is accredited and I'm confident the Glendale program will likewise receive accreditation. The only remaining downside to the private schools is the relatively high (compared to NAU) tuition but I'm prepared for that if I have the opportunity to attend.