Thing I’d like to see in Tiger (OS X 10.4):

Better keyboard support – it’s really sad how tabbing through dialog boxes (and checkboxes!) works (or more specifically doesn’t). Even when it sort of does, they all work differently (sometimes its arrow keys, hot keys, or tabs. wtf?), and having the space bar and enter key do different things is just bizarre
Fonts are a mess regardless if you’re using the Fontbook or a third party app like Suitcase. Love how random Cocoa applications get their text completely gibberized/overlaid with lots of fonts.
Powering up/down – it’d be nice to schedule auto-mounging (based on location) on powerup and wakeup. Also, would be interesting to autodetect location when possible based on network. Have some thoughts on writing a util for that, so if it doesn’t come I may end up getting a chance to write one
X11 – multiplane windows, transparent window support, dock icons per applications, keyboard buffer binding (honestly, can it be that hard to add a cmd-v?)
Better application binding support — I’ve started popping off Applescripts, which are fine except for the creator code binding totally screws up ‘default application’ binding
iCal – actual pubsub
AppleScript – better GUI scripting; macro recording