Anyhow, of all the features that the new Android offers…the performance enhancements made possible by the use of JIT (Just In Time compiler for the Dalvik Virtual Machine) is quite possibly the most important.
Here is why
The JIT is a software component which takes application code, analyzes it, and actively translates it into a form that runs faster, doing so while the application continues to run.
Code that is written to run the CPU all-out can now do more in the same amount of time (running faster), and code that is written to be rate-limited can get its work done using less time and less of the CPU (using less battery). On the performance front in particular, we have seen realistic improvements of 2x to 5x for CPU-bound code, compared to the previous version of the Dalvik VM. This is equivalent to about 4x to 10x faster than a more traditional interpreter implementation.
Read full post from Tim Bray on Android Developers
You read that right…2x to 5x faster performance! This is what really counts when you are trying to surf the web, upload/share photos, send/receive emails, send text messages etc.