I'm with most other people on the size question...check out the Medium. I use it with 30 inch monitors. This smaller size enables you to leave the nice compact Apple keyboard in front of you too. I have the Wacom closest to me and the KB right behind it. Don't cheap out...get the Intuos.
But here's the interesting bit. If you use a Wacom Graphics Tablet and also tend to use a lot of keyboard shortcuts, there's a productivity tool that has transformed the way I work. It's the Nostromo from the gaming device company Razer. http://www.razerzone.com/au-en/gaming-keyboards-keypads/razer-nostromo/
If you have a Wacom and don't use it very often, this may be the perfect companion to get you to use it all the time. It's comprehensively better than using the buttons on the Wacom. The only button I use on the Wacom now is the Touch Ring for brush size.http://www.pwp3.com/nostromo.jpg
This image shows how I have it set up. Of course there is a mouse (Razer Death Adder) on my right as well. The Wacom, the Nostromo & the mouse don't conflict with each other. When you have the Wacom pen in your right hand, it's brilliant to have a scroll wheel and an enter key on the LEFT side. Plus, every one of the buttons on the Nostromo can be custom configured to execute keyboard commands...single keystroke keyboard shortcuts. You can set up a custom set of commands/macros for each program that you use, like the Wacom. So I have a set for Photomechanic, Lightroom & Photoshop. The Nostromo detects which program you're currently using and switches more or less instantly. If you work through large folders of images every day, this gadget will be your new best friend. I doubt Razer had non-gamers in mind when they made the Nostromo, but hey!
The only downsides are that your teenage kids will want one for themselves for gaming. But the cost is around the same as a decent mouse. The irritating teen focused blue glowing lights can be turned off. You save your settings with Razer's cloud solution, Razer Synapse II which also stores my mouse custom settings. I've bought another Nostromo & Wacom for a second workstation and Synapse II sure beats having to manually configure each command and macro again.
So there you have it! For me this is a cool toy and a powerful productivity breakthrough.