Sure you can use a tablet. I don’t think blender supports pressure sensitivity though, not that there is much to use it for outside of vertex or weight painting.
There is the sulptmesh script that can access pressure sensitivity as well.
Is it worth the investment just for blender- no. However, if you plan on using photoshop or gimp or sculptmesh or I believe Zbrush with blender, then it could be worth a look into. It saves a lot of time when painting textures, believe me. So if you plan to ever use UV maps (which you should) then you almost certainly are going to want one.
I still do most of my modelling and blender work with a mouse though.