It depends on the machine you use. You will need to have at least an Intel-based Mac in order to use Snow Leopard. Go to the Apple-Menu and select “About this Mac”. You will see a line saying “Processor”. It will either be something Intel or something PowerPC. If it is the latter, you will have to remain with Leopard which is a great system. If it is an Intel, you are in luck and should definitively update to Snow Leopard. It is much smaller in space on the hard disc, so extra room for more music or family pictures. It is a good refinement over Leopard and the update is exceptionally cheep.
You will profit even more from Snow Leopard if your Mac’s processor can handle 64bit computing since this is one of the main features of Mac OS 10.6.x: full 64bit capabilities. Not all (Intel) Macs can do it. To check if your’s will do 64bit go to the Terminal applications (usually in Utilities) and enter this line:
sysctl hw | grep 64bit
The Terminal should answer back with either hw.cpu64bit_capable: 0 or 1
If the answer is hw.cpu64bit_capable: 1 this means Snow Leopard can use all its capabilities on this computer and you will most likely already note that finder windows do open much much quicker after you updated. Other apps will also profit. But there are downsides to this:
Safari e.g. will work in 64bit mode. If you are using Google Gears (the offline webbrowser database from Google, to allow things like speeding up WordPress blogs’ admin area or allow for offline access to Google Mail accounts etc) the 64bit mode will break Gears. You won’t be able to use Gears any more on 10.6 since they still haven’t updated their plugin to be 64bit compatible (well this is the short story, in reality this is a much more complex thing as it has not only to do with 32 or 64bit mode but also with the way how in general plugins should work in Safari)
But even if your Intel-Mac is not 64bit, if you HAVE an Intel Mac (and not a PowerPC based Mac), GO for the update to Snow Leopard!