In just a few months, Firefox jumped from version 4 to version 7 without any significant visible changes to the browser. Although Google Chrome does this all the time, it doesn't have the problems Firefox faces with every update -- extensions compatibility & administrative headache.
While users rejoice for new features Firefox introduces with every update, they face the problem that a lot of their extensions stop working until their respective developers update them. The funny part is that even if the extensions would still work with the new version of Firefox, they are still shown as incompatible because of the maxVersion setting.
It's even a bigger nightmare to system administrators where they find it hard to cope with the frequent updates they need to push to their users with every Firefox update (Chrome on the other hand doesn't require administrator access to update!). To remedy this issue Mozilla is considering a not-so-rapid-release version of Firefox which in my opinion makes the problem even worse because it adds to the fragmentation problem the browser is already having.
So what would've been the best strategy for Mozilla?
If I was in charge of Firefox I would've pushed Jetpack into the browser by default in version 4 & started to encourage extension developers to convert their extensions to that format. This guarantees that all extensions would continue working normally under any future version of Firefox, just like Chrome extensions do. When the majority of popular extensions move to the new method of writing extensions, I would start introducing the rapid-release updates & slowly phase out the XUL way of doing things (XUL also makes Firefox run slower than the rest of the browsers).
That said, I'm really looking forward to see Mozilla's next move, it's a very tricky time for them as they are noticeably losing market share to Google Chrome.