Oh that's true. I bet you'll be happy with the purchase, whatever it is. For me personally, I tried using Macbook like this. Well not with Thunderbolt/Cinema display but I had an Arc dock, external stuff attached to it.
It wasn't bad but I felt like it's such a waste of money/resources because my laptop went with me only like a once in two months. I decided I wanted something more powerful and not laptop again.
I must admit I finished a circle. Started on PC towers because of power and expandability, then went to laptops because portability was a plus at the time I was a student, lived in a dorm and used to go home every weekend.
Switched to mac in Uni 2 years ago, portability was still a plus when I took it to classes but not a necessity. For past two years I started doing little freelance stuff with HD video and discovered that I needed more computing power and fast storage. But I'm still on a budget so no Thunderbolt RAIDs for me.
Seriously considering getting used Mac Pro or hackintosh because now I see the tower as a plus again, I already have a laptop covering my portable needs which are only few occasions in a single year.