Lion is as bloated, if not more bloated, than Windows 7. So many unnecessary processes running compared to Snow Leopard.
While this "Windows runs with so much unnecessary garbage, security risks, and unnecessary legacy code was true for a long, long time", Windows 7 really took care a lot of it.
I certainly think that there is a lot of room for improvement with Windows, as I think the same for Mac OS X.
I really don't know how Windows 8 is going to turn out. I have no idea. In theory, it should be awesome. A full fledged OS running on either tablets or desktops, able to be installed on ARM processors, etc.
The reason why Microsoft failed with the tablet for so many years was because they were trying to build it to be like a computer. Steve Jobs himself said this at Everything Digital 2010. This led Microsoft to allow manufacturers to slap Windows on a half-baked, heavy, tablet with the x86 architecture (which is extremely energy inefficient) with minimal UI changes.
Instead, what Microsoft is doing with Windows 8 is making an OS that is full-fledged windows, but allowing a switch between a dramatically changed UI for tablets (which has proved very successful for Windows Phone), and full-fledged Windows that everyone knows how to use.
I am not sure how it is actually going to be, though. The biggest thing is supporting two architectures, x86-64 and ARM. This isn't a transition from PPC to x86. This is a coexistence of two architectures at the same time.
My point is: Don't criticize an OS that is in very early betas. Lets see how it plays out.