Trash iChat, and replace it with Adium with file transfer/sharing. Bingo, hands down, best chatting on the planet.
Also, lemme turn off all this eye candy transparency/throbbing/dropshadow madness. Please. I need to wring as much power as I can out of these ol' G4 chips. Although I won't care once the 970s are out anyway. And with quartz extreme... well... I guess its okay.
Let's see what else.. better list view. The list view in 9 looks a lot more orderly with its rows and columns that this plain white stuff.
User-creatable themes would be nifty.. but eh.
Improve Coreaudio/Coremidi. I donno how, just do it. Find some problems and get fixing.
What else... let's see... how about like a preferences option or something for like POWER FINDER which lets you use the finder like OS 9. No more telling me I don't have permissions to move stuff. I said move damnit!!
How about a Notepad revival? I loved that app, and all the 3rd party ones for X have "features" and other stuff. Who wants that. I want flippy action and typey action.
Uhh... animated icons?

Or do we already have that. *ponders*
A less stupid open/save dialog? Damn that thing is annoying. Think about it. It's annoying, isn't it?
Maybe have the Applications and Documents folders not be such nazis?
Uh... amazing new audio/midi internal routing stuff.
White or brushed metal, make up your mind. I say pinstripe everything. I love pinstripes! The brushed metal looks tacky though. Especially iChat, which is like Tacky central, in about a billion ways.
Basically, kill the brushed metal. The software tries to look like metal, while their hardware tries to look like white plastic. It makes no sense. Also, the iApps have brushed metal, but the iPod and iMac are white. However, the pro apps don't have brushed metal, yet the Powerbook does. SCARY, no?
FIX THE BRUSHED METAL INSANITY!
I donno, it's late. Just fix stuff and give me a few new features that are actually usable, like full spring loaded folders that allow the "click an a half" like OS 9 had. Although I guess its not needed with this new one window finder stuff.
I just don't like dropshadows. They make things feel cluttered. Ick. Turn em off!
What's the shareware app that does this? Ah I'll go check version tracker.