From Android in general, I just want better battery management. Better efficiency. Battery life should be better these days despite everything getting bigger and better. There should be a way to have a great performing phone that actually last you a day or two just fine. That, and a unified message service similar to what iMessage is. These are just Key Lime Pie issues for me that I hope it addresses.
Hardware has stalled a bit as many threads have already been written about. Hardware has never been my main concern with android anyway. Efficient software will make any hardware fine. You can't tell me the S4 is VASTLY better than the Nexus 4 in every day usage, performance wise. Jelly Bean and project butter for the most part make all these phones feel smooth.
Key Lime Pie needs to put Android over the hump, seriously. Aesthetically, things improved greatly with ICS. Jelly Bean brought smoothness and a killer feature like Google Now. Key Lime Pie needs to damn near eliminate lag. Unified messaging. Hopefully software improvements for the N4 camera. Minor aesthetic improvements. Thats it. Google can cement Android has a sure fire legtimate replacement to the iPhone with just a couple key features. Make it happen.