Its not just start up time (only relevant on reboot or VS crash), its the amount of time it takes for VS2010 to page back in after being idle for a few hours, its the amount of it takes to edit a file, the amount of time it takes for code completion to activate, the amount of time to build your project. I'm only comparing 2010 to 2008, Microsoft's biggest competitors are often its own older products!

We can speculate all we want on what the deal is with VS2010; I'm just happy 2012 seems faster.