Testing, timing and more testing. Most manufacturers have their own user interface and it takes time to make it work with each new version of Android. Plus Android is still not a trusted product in some minds. It’s like buying the first version of a new model car and kicking the tires after it starts to act up. Older software works better because the bugs have been worked out. ICS is still new, there will be bugs.
Let us know if you feel the same or differently.