This is the list of updates/improvements that Apple says is included in this update:

* Decrease in call set-up failures and dropped calls
* Significantly better battery life for most users
* Dramatically reduced time to backup to iTunes
* Improved email reliability, notably fetching email from POP and Exchange accounts
* Faster installation of 3rd party applications
* Fixed bugs causing hangs and crashes for users with lots of third party applications

* Improved performance in text messaging
* Faster loading and searching of contacts
* Improved accuracy of the 3G signal strength display
* Repeat alert up to two additional times for incoming text messages
* Option to wipe data after ten failed passcode attempts
* Genius playlist creation

There are important improvements in this release as you can see from this list like better battery life, fixes for bugs that crash iPhone and improvement on dropped calls.

For more information check Apple’s website.