So in other words it's still slow but because of vendor pressure it's been lumped into "The OS" to hide that cost from the user?
More overhead is a tradeoff you make to use a VM. I think it's worth it usually but it is there.
I only used it on a Mac, before I discovered plugins that did Facebook integration for iPhoto (and later, that was baked in). And on OS X, no, it was not slow. I'm assuming it would be equally fast for windows.
Also, its not so much lumping the start up cost to "the OS" so much as "The OS Starting Up". How often do people reboot their machines nowadays? Once every six months? With that in mind, it's a pretty negligible trade off.