The anti-enterprise position was never the official view of Mozilla; it was something expressed by a few employees of Mozilla. There are certainly plenty of others who feel quite differently about it, as you can see from reading Planet Mozilla. I don't think Mozilla has expressed a position on any of this.
For example, here's a counterpoint view. There's some good points there. The main point: major Firefox releases that include important bugfixes were taking more than a year to come out. This was very bad for many groups of people. Point releases took 6-8 to come out, but without too many major changes (the idea that Firefox point releases never included new functionality is false - out-of-process plugins came in a point release.) Mozilla has now simply merged the two: the only releases will come out every 6-8 weeks and will include whatever's ready, like Chrome.
There is, in fact, a stable extension API called Jetpack. The problem is that Firefox extensions can literally do anything at all to Firefox, access internal APIs and do whatever else they want. An external API like Jetpack is no good for that. There's a tradeoff. AMO bumps compatibility on most extensions automatically, but not all. So some extensions will be temporarily incompatible (personally, I didn't have any issues - about 15 extensions). On the other hand, users will get, for example, the massive memory improvements coming in Firefox 7 in a month or two rather than sometime in 2013.