I love my tablet (iPad), and now that I have one don't want to live without it.
My notebook makes me a bit more productive, but it's kind of an evil necessity. All the complexity of a desktop, but not as useable with it's sub-par keyboard and pointing device. I whip it out when I need to, but at home it stays mostly on the shelf.
My desktop with nice big dual screens and full keyboard and mouse is where I'm most productive, and where I go if I need to do some real work.
So, at home when I'm using some kind of device, I'm on my tablet say 47.5% of the time (nights and just hanging around the house), my desktop 47.5% of the time (when I'm working), and my notebook 5% of the time (when I don't want to be in my office but need to do something my tablet can't handle.
When I travel the tablet is nice, but I don't dare leave my notebook at home.
I don't think the tablet will replace the notebook, but for me it ALMOST replaces it at home. 50/50 when travelling. Neither will ever replace my desktop.
As for docking stations, they're nice if you want to use your notebook as your main PC (I don't), but you need to get a REAL docking station. In my opinion USB docks are crap and barely worth it. Dedicated docks are great, but you have to buy a higher-end notebook in order to have a docking station connector. Also, they typically overcharge for most docks. It's nice, but expensive in the end.