The thing you'll want to decide is, do you want a "covertible" Tablet that will double as your notebook, or do you want a "slate" Tablet  that is lighter and thinner, but not so good as a full time machine (in my opinion). 

The best setup - if you can swing it - is to have one Notebook/Desktop as your primary machine (non-Tablet) and a "slate" style Tablet PC for taking notes, drawing, etc. 

For a convertible I think the Toshiba M400  looks good.  I had an earlier model of this and it was nice.  For the slate style the Motion Computing tablets are awesome.  I have a Motion M1400 and it is great. 

I got a Toshiba Tecra M4 at work and did not like it at all.  It was nice and powerful, but I found it too big and bulky to use as a tablet, the fan was very noisy and on all the time, and the battery life was awful (1.5hrs)

p.s. for most of the slates you can still get a docking station and connect a keyboard via USB ports.