So, can you use these Wacom tablets as an alternative to a mouse?
Depending on your monitor setup and the kind of work you're doing, it's not only an alternative, but a much better choice.
Sometimes I'll connect mine (Intuos3 A4) to one of my computers just for something graphics related, and it'll will stay there for a few days without me even noticing I'm not even using the mouse, until I need to use it on another computer. Also, I usually use only the bottom half in a dual monitor setup and the right-bottom quarter with a single monitor setup (even with my 30"ACD). The top half is where I put the keyboard so that it's always next to my hand.
It's great for everything graphics related, but also as a general pointing device, and with some imagination (shortcuts, macros, keyboard placement) can even get into things more technical, where a mouse is the norm.