I love MPR's BUT... when irrigating large areas they are not the best option. On large systems it can increase the overall run time on the clock 3-4 hrs. This means you might not be able to get through a whole cycle in one night. Usually that is not a problem, but in drought prone areas (like Austin) that is a big deal. If you only have 1-2 watering days and you cannot get through your whole system in the given time period it is not good.
We use MPR's on 90% of our jobs, but when it comes to large irrigated areas we stick to the PGP/5004. If it is any consolation we used LA nozzles.
Also with the MP's you can price yourself out of a large job quickly. Even though the MP3000 is supposed to spray 30' they are only effective out to about 26' spacing. That is a lot of extra heads when you can space rotors much further apart.
I agree with you, and try to use water saving products as much as possible. Every product has it's application though.