Wow, I never noticed how loud depressing the spacebar is until I saw this thread, it is loud!
I can't really think of that many cons, I guess it seems like it takes a while for the battery to charge? That might just be me though.
I'm finding the biggest pro besides speed is the new trackpad, I love it and use all the new features. I've also been using a program called Multicluth to assign specific mouse gestures to individual programs.