virtualbox.org

Just installed Guest Additions and the highest screen resolution option I get is 1400x1050. I'd like to set it to my MBP resolution which is 1920x1200?

ohh... that's interesting, I just switched to full screen mode and it switched to 1920x1200

That's right there are two different full screen modes. One is windowed and the other is not. host+F is the true full screen toggle.
Clicking the full screen (windows clicks) will read smaller but allow you to see the title bar. Use the host+home toggle to see the VBox menu if the mini toolbar does not work properly.

Yep.. all good now Perryg.

BTW Virtualbox seems to run snappier than Parallels or VM Ware from my experience?

Yup and there is a whole lot more that you still need to find. VirtualBox has a lot of bells and whistles. Just bookmark the following link:
http://www.virtualbox.org/manual/UserManual.html