Probably the single greatest flaw of OS X, from my perspective, is how it renders large monitors so much less effective than two medium size monitors - nobody I know would prefer a 30" monitor to two (2) 24" Monitors - If someone could only write a windowing manager that converted a single large monitor to two simulated physical monitors, that would be a start. Even better would be to recognize you need to treat a 30" Monitor differently than a 17" Monitor from a windowing perspective.
That and get Terminal.app to actually _tile_ sanely. If I had a _single_ feature request for 10.7 - it would be a window manager that gave you sane tiling capability.
Arguably in the Windows world this is even worse. The default reflex in Windows is to maximise every window you have. At least with on OSX the default way of making a window bigger is just to "zoom" it to a better size.
Also regarding tiling terminal.app you should really have a look at GNU Screen. You can use it to create multiple sessions in one window that are split in a 'sane' way.
That and get Terminal.app to actually _tile_ sanely. If I had a _single_ feature request for 10.7 - it would be a window manager that gave you sane tiling capability.