The battery life on my 2nd gen iPod touch doesn't bother me that much because I have chargers pretty much everywhere I go.
What bothers me is:
* Lack of multitasking (so slow to switch between apps so I often miss out on entering free app codes. ;-)
* Inability to remove certain stock apps which I NEVER use
* Lack of unlimited pages and the inability to delete apps directly on the iPod from the spotlight search
* The slowness/freezing of iTunes for Windows when dealing w/ large numbers of Apps
* The lack of a built-in microphone and/or camera
Really looking fwd to July when I finally purchase my first iPhone!