I upgraded my MacBook to Snow Leopard, that's OSX 10.6.
Let me tell you that I notice almost nothing different from 10.5 Leopard that I had been running. I remember when I got Leopard -- it felt like a whole new computer. On the other hand Snow Leopard cost $29 (as an upgrade from Leopard), and Leopard cost $129.
There are not too many changes. The biggest thing is that it boots up faster. I timed a restart in 95 seconds. Finder works a little differently, and there are more file preview options. Nothing earthshaking.
They say most of the features are "under the hood." I think most of the features are for people running multi-core processors and native Mac Apps.
No doubt it is best for the new super-cool Mac Pros running twin Xeon Nahalem processors, each of which is a quad-core processor. I have no reason to run something this fast, but sometimes I wish I did.
Apple, unlike any other company assigns cool little logos to boring internal operating system functions, like "Grand Central Dispatch," which routes instructions to the different processors. It is like Microsoft giving a logo to sfc.exe.
Supposedly, Flash is supposed to run twice as fast. I tried some experiments, but I could not convince myself that Safari was loading Flash pages faster than Firefox.
Anyway, I wanted to get Snow Leopard because my policy is to keep the software current to avoid problems. I think $29 is better than spending a Saturday debugging some software. Of course it does not help me that my favorite application, Microsoft Excel, is still a buggy, non-native application.
The coolest thing about the Snow Leopard is the packaging. All the Apple packages are wonderful. I still have my iPod Nano box. I photographed the Snow Leopard box above, and then downloaded the image below. The white box and smart graphic design make you think you are getting something valuable and cutting edge.
How did they get the leopard to hold still while they blew snow on it?