1. You don’t need to have Leopard already.
Yep don’t think you need the full box set. You can just purchase Snow Leopard to upgrade from Tiger. Also if you bought your Mac on or after June 8th you can get Snow Leopard for $10 on the Apple up to date scheme.
2. Traveller clock
Go into Date and time preferences and you can check "Set time zone automatically using current location”. Perfect for those that travel around a lot with their Mac. Third party apps will also be able to take advantage of location support.
3. 64bit my Mac
If you want to boot into 64-bit mode hold the 6 and 4 keys on startup. 64bit programs will start up slightly faster in this mode.
4. All you Sync belong to us
You can now Sync your Google and Yahoo accounts via Address Book > Preferences, Accounts tab. iCal will now syncs with Google and Yahoo Calendar. Also of course it now supports Microsoft Exchange servers one of the biggest features of the upgrade.
5. Where is my Clean Install
Sounds like Apple had more than a few people call up and complain about where the #$@$ there data was. So you can no longer select the friendly sounding clean install instead you will have to go to Utilities > Disk Utility.
6. Check scanner and printer support
Not much more annoying than not being able to print so you might want to make sure your printer and scanner are supported before you upgrade. There is also a new auto update feature for printer drivers so when your printer is supported you should be set.
7. Boot camp buffed
You can now view your Windows files and vice versa your Mac files while in Windows. Handy although restricted to read only access for now (will keep an eye out for hacks around this).
8. Give me my hard drive back
Results vary but you will definitely claim back hard drive space by upgrading between 5-10GB.
9. Wardriving just got easier
When you go to select a wifi network you will now get a handy icon next to the connection name showing the signal strength.
10. Wake up
You can now wake servers when data is needed if they are in sleep mode.