Triplexcash is using MPA2 now.
In fact we just started, and I am still playing with the admin area.
It's pretty impressive.
I wouldn't call the use of such software a trend though. This kind of thing has always been done. The major difference now is that when we go to a 2nd or 3rd processor because of decline, we are no longer permitted to carry over the credit card information. Everything else (name, etc..) is fair game, but they have to fill out the CC info again.
Still, it's well worth it to use such a system and can immediately increase your sales by 20%.