I, too, consistently run Solidworks on my SP3 and I love it. The ONLY thing it cannot really do is fine renderings with RealView Graphics because of the GPU. Other than that, for 3D modeling and a pretty decent amount of engineering, it is wonderfully adequate.
I also have the wireless version of 3D Connexion 3D mouse and it is fantastic.
My current best hack is to crimp the pen holder and put it on the kickstand. It presents the pen to you like a real pen holder at almost EVERY angle the kickstand gets set to (except when approaching fully back...then it gets a little akward), and folds flat when the kickstand is flat.
Good luck!