Finally, a Windows mini-tablet for pros. With Microsoft enabling portrait-oriented mini-tablets in Windows 8.1, PC makers have responded with several decent consumer-oriented devices. But the ThinkPad 8 is the first Windows 8.1 mini-tablet aimed at business users. And as I evaluate it over the next few weeks, I'll try to determine whether it lives up to the vaunted build quality of other ThinkPad devices and justifies the additional expense.