While I agree with Gully, that a 3-button mouse is ideal, I use a Wacom for SketchUp and have for years, it’s a personal preference for me.
The main consideration with a Wacom vs mouse is navigation. Personally I have mapped orbit, pan and zoom to keyboard shortcuts and used this setup very successfully. I know of a few other wacom users who also use 3dconnexion device for navigation, and that works well for them. If you do use keyboard shortcuts as I do, you lose the precise zooming that comes with scroll-wheel zooming. Not a deal breaker, just fyi.
For me, using a mouse all day cramps my hand up something fierce, so a wacom is a good alternative, I much prefer it at this point, but again, it’s mostly a personal preference, and is a bit more limited if you also use LayOut frequently, so again, completely agree with Gully that SU is optimized for mouse, but a few of use still love our wacoms!