To echo what many others are saying, Snow Leopard is not primarily designed to address the shortcomings of Leopard. It's nothing like what Microsoft is doing with Windows 7. That said, even Windows 7 is more than a service pack.
Apple is introducing some significant new technologies that will be overlooked by many, many users simply because they do not understand the technology behind the operating system. Please note that this statement is not an attack at anyone on this board. Apple would have very limited success advertising that, with Snow Leopard, your GPU can assist with tasks that were limited to your CPU in the past. Likewise, they are not going to explain why all cores are not running at 100% all the time.
The technologies introduced with Snow Leopard were never owed to users when they purchased Leopard. These are new technologies designed to better use the hardware that Apple has been releasing recently and will be releasing into the future. The operating system is the platform on which everything else operates. Thinking that Apple failed to deliver in the past because your hardware is running at less than 100% efficiency today suggests a lack of understanding of systems in general. Again, this is not an attack on anyone here in particular, just a response to what seems to be a general opinion of the update.
I'm not sure what my point was with all this, but those are some of my thoughts on the matter. Snow Leopard may seem boring on paper, agreed, but excitement does not always equate to value.