The things I'm most excited about are mostly pretty simple stuff:
-The new home screen with resizable tiles to fit more (which we'll get in 7.8! Yay!)
-Separate volume controls for music/ringer/alerts
-Faster, more robust app switching/multitasking
-Lockable screen orientation
-Support for higher resolutions. I really want 1280x720 on my next phone.
-Apps: Specifically I want Citrix Receiver and some 3rd party browsers that ARE NOT based on IE.
If it has all those things, I'll be very happy.
Some "would likes" but not critical for me:
-Folders, and maybe a way to store files locally in folders that will auto sync with SkyDrive.
-Better games. I don't play games on the phone much now, so it's a minor point, but I'm sure WP8 is going to bring some great ones.
-Ability to re-map the search button to Google instead of Bing (sorry Microsoft) unless Bing gets A LOT better. Unless you're going to do something amazing with Bing and soon, please let me choose my own default search and let me re-program that button. Aside from image search, Bing doesn't equal Google on anything at this point. I might even want to reprogram that button to launch IE or another app. Would be nice if I could do that. Not a deal breaker by any means though and I know there's a snowballs chance in **** that Microsoft is ever going to relinquish control of the magic BING button.
-I'd love to see some native built in Log Me In type remote access, so I could interact with my PC, easily do things on it, stream video from it, download/upload files. I use a Mac now primarily, but some really cool WP8-->Win 8 features like this could convince me to build myself a desktop PC for home use.
The rest of my wishes are more hardware than software, i.e. a PureView camera on a Nokia phone with 1280x720 resolution and a 4.3" or smaller screen (slightly smaller form factor than the Lumia 900 if possible, or at least no bigger)