I recently decided to move to mp2 because early adoption can put you ahead in the job market in a year or two. mp2 relies on apache2, obviously, which as you may know is really well thought out as an Interenet application platform and not just as a straight webserver. mp2 also looks like it will be *drastically* easier for webhosts to support so, with some luck, it will regain the traction it's been losing.

I've had no stability problems with mp2 at all, though I've done only the smallest applications with it so far. It has lots of new goodies for coding and simplified interactions with Apache. More at the perl.apache site; starting with 2.0. I don't personally know anything about MPM but there are lots of references to it on the mp site if you do a search.