Even with a defrag Ref it's slow. I ran my GWX career lastnight after a fresh defrag and it was still slow loading.
I've got 2gigs of RAM, a P4 3.2E CPU and it's still slow. I figure it's due to all the chnages incorporated in GWX, which isn't all that bad considering what we have. Single missions are actually slower than my career. I'd say it's something we just have to live with.

And I don't mind, I like GWX just the way it is.