"Fairly useable" is a wide target. It depends on the type of files/assemblies you intend to create. SW will run on a wide variety of machines but there are no guarantees of success unless you follow the recommendations on the SW Hardware requirements site.
I know quite a few people who love the SurfacePro2 (or 3).
Beyond that, and as Jeff mentioned, find something that follows the recommendations here: SOLIDWORKS System Requirements | Windows and Mac | SOLIDWORKS