1. Quicktime 7 - H.264 As an editor, QT is the biggest reason for me to upgrade to Tiger. I use Quicktime all the time, as it is essential to the apps that I use, notable Final Cut Pro and DVD SP. The best new features of Quicktime Player, is that it is completely multi-threaded, so exporting does not tie up the program. Support for H.264. H.264 is an amazing new codec! I love it. At about 1.5Mbps, the quality is nearly indistinguishable from MPEG2 at 6Mbps and DV video at 25Mbps. I love this codec. 2. Finder Finder is more compact, smarter and faster. +50% by some estimates. 3. Spotlight It's wickedly fast. And since it searches the contents of files, even if you forget the file name, you can definitely search within the files themselves. I use it to search within emails, such as if I want to find phone numbers hidden inside email messages. And Spotlight is only a Command-Spacebar away, giving access to seach within a keyboard command. 4. Dashboard I love the fact that it disappears when you don't need it and appears instantly when you do need it. Great for little apps such as calculator, stickies, weather, conversions, and address book. No more fishing inside the applications folder to launch the right app. Its just F-12 away. It's amazing we were able to live without Dashboard for this long. It's very much an integral part of OSX now. One issue I don't like are the widget icons down the bottom are too big. Apple should cut the size of these icons down to half their size so you don't need to sideways scroll to look for more widgets. My other complaint would be to cut down the strength and duration of the ripple effect. Or give us the preference to turn it off or reduce the ripple effect. I love the effect, just it's too strong. 5. Mail The new Mail interface is just plain sleek and gorgeous. Thank god they are starting to phase out drawers. Drawers are so ugly. Mail is simply gorgeous. Enough said.