Well Jon, Vista definitly loves RAM for caching reason. I personally have 4GB and I never wait for any apps to launch 'cause they're already partially in memory ready to be launch. That's for regulary used apps, the system "knows" it and put thems in memory, in a waiting state ready to be fluched out as soon as that memory space is needed by other apps.
Looking at it this way, your friends computer is for sure faster at launching apps, but maybe not at running them. All it does is make your system feels/be much more responsive, not faster.
Vista isn't perfect, but I sincerly think it'll be the system to have after SP1 if Microsoft does it's home work. On my side, I didn't have the choice to get it for long term useability of my new system. I only relay on XP whenever I want to play oldies, but anything newer then 12 months worked flawlessly until now.