Search option. The whole keywords system is lame. But I guess we'll see Spotlight integration with iPhoto 5 and Tiger.
Performance is ok but why does it take 5 seconds to rotate an image through 90 degrees? My Amiga 500 rotated pics quicker than that.
Make the bar at the bottom customisable. Also, I know it's a general feature of Cocoa apps but, I hate it when iPhoto is in the background and say I'm using some other program (e.g. Safari)... If I click on part of the iPhoto window to bring it into focus and accidentally push part of the "iDVD" button or whatever, it will start processing that function - i.e. launching iDVD or whatever when all I want to do is switch programs.
Update the book system. More choice is good, plus how about a save option? It looks as though most of this hasn't been updated since iPhoto 1 was first released and it's all a bit Mac OS 10.1-like. It's a bit cumbersome to make a book at present, plus how about it being a bit cheaper?
View any photo in full screen option.
Fix the bug which means the photo title or comments text box sometimes and unpredictably loses focus while typing text in them. This has occasionally caused me to accidently delete a photo (luckily only to the trash) without really realising it. *PLEASE APPLE PLEASE* This bug was not present in iPhoto 2.
Option to rename actual filenames and make the folder system better. Still allow current file system to work to maintain compatibility with iPhoto photo CDs or DVDs (ones which have already been burnt).
Ticks confirming star rating in contextual menus consistent with iTunes. (Nitpicking now

)
Better presentation of titles when displayed in slideshows. Currently they have a crummy black background and are displayed at the top left of the screen and currently look so unprofessional that I never turn them on.
iPhoto slideshow music to take account of iTunes Sound Check option (so all music volume is the same - this applies to iDVD too).
Hmm.. that'll do for now
