i have a laptop and a desktop laptop for mobility and desktop for some more demanding applications....
I am using laptop, and I like it much more then using desktop... Laptop can always be used as desktop computer, but desktop computer cant be used as laptop.
I rock a MacBook Pro with an additional LCD mounted to the wall behind my desk. Gotta manipulate large chunks of data? Gotta update code and preview results quickly and efficiently? Get another screen. It's a lifesaver. Couldn't lose the portability of my laptop, either.
I use my laptop most of the time. I don't have a desktop and I don't have any plans of buying one until I have my own house. So long as I travel and without permanent address, a laptop will travel with me.
I am on desktop now. I used always desktop and never use laptop. Desktop is very easy to use for me and I can do fast work with desktop than laptop.