Release early, release often... In my opinion its worked great for the Kernel folks since v2.6 was released. Does anyone remember the hell that was upgrading from 2.2 to 2.4, and again to 2.6?
The more things that change at once, the greater the pain will be, its as simple as that. Holding back all changes and releasing them all at once with a major version upgrade causes the most pain as possible, and people are reluctant to actually upgrade, so testing is limited.
Instead if they release small changes more often, they will get more testing as more people are willing to risk an upgrade if only a small number of changes occurred, and if something does break, its limited in scope. The key here is that you try not to upgrade too many important parts of the system at once. For instance Xorg should probably never be upgraded at the same time as KDE/Gnome if possible.
For example, if Apache releases a new major version, you can send that out and if something breaks, its pretty easy to roll-back or fix the issue, since only Apache was changed and maybe a couple other minor things.
Instead if you upgrade to a new version of the entire distro, if Apache breaks you don't know if its directly related to Apache, or one of the other 1000 packages on the system. It makes troubleshooting, bug tracking and quality control much more difficult.