I suggest you use the powerful
search function of this forum with "MCACC" or "YPAO" as query. You will get numerous posts such as the ones in
this recent thread. While a person (mwc) describes a negative experience with the MCACC in the thread, I myself, like quite a few others here, am extremely happy with my Pioneer 45TX's MCACC feature. So, back to your questions:
(1) Only you can really answer this one. However, I have to add that in order to fully appreciate the benefits of MCACC/YPAO, you do need to listen to it in your own room, although you can certainly experiment in a well-isolated dealer showroom, if the dealer is fully willing to let you play around with his equipment.
(2) The YPAO still being a few weeks old on the market, the jury is still out on this one. However, at least on the specs, YPAO's 7-band "parametric" room EQ is more advanced than MCACC's 5- or 9-band fixed EQ. Third-party measurements on Yamaha's amp sections are still forthcoming, too; Pioneer's amp section has been shown to be VERY robust by independent measurements.
(3) Yes, there are several standalone automatic room EQ/real-time analyzers available, especially from the "pro" market with quite affordable prices, such as the
Behringer DEQ2496. However, you have to know what you are doing in order to incorporate these pro gears in your home system, with regard to details such as signal-level matching etc. Also, these are 2-channels only products.