The biggest factor seems to be the huge jump in the code base between Gingerbread (Android 2.3) and Ice Cream Sandwich (Android 4.0). The CM team indicates that they more or less started from scratch with the ICS build of CyanogenMod (CM9), and have been porting their CM7 customized tools to the ICS code.
While this process takes longer, it’s also allowed them to rethink each step in the process – an example is they will be eliminated the CMParts app, instead they will be exposing the custom features directly inside the main settings menus.
The CM team also is embracing a more user-driven UX, trying to make many of the features “just work”. They felt that CM7 was unduly complicated, with many obscure options that were rarely put to use. Now they feel they are striking a better balance between user customization and a really good out-of-the-box experience. The result should feel like CM9 was intended to ship on your phone, rather than an open source OS that was hacked in at a later point.
So there is a lot to look forward to, it’s just not happening as fast as some people came to expect during previous builds. Not that the CM team expects to be late to the party, they just won’t be as early as they have been. Or as they put it: “As much as we’d like to stay ahead of the manufacturers, it may be a tie this time.”