One reason I like my MacBook Pro so much is that I'm never tied to a desk. When I work from a desk productivity/motivation to work dwindles fast. With my MBP in hand whether it's on the couch, kitchen table, outside, coffee shops etc I've all the motivation in the world to get things done. I find it odd, but apparently there's a word or term for it, some people like to lean in or forward to read and work, others need to lean back to read and work to feel comfortable, some need solitude and a desk, others such as writers prefer a public cafe or couch at home, I'm in the later. I wish I could feel comfortable at a desk, to enjoy a 24" in screen over 15" is more productive of course ... perhaps too many years of stress working at a desk to the point the thought of it drains my desire to be productive or creative. Best idea's come to mind for me when I'm relaxing on the couch with my MBP on my lap.
Mostly on my desk while I'm studying, makes it easier to use both online notes and printed stuff. However, I do have a computer desk as well, where it gets mounted on an mStand with all my external peripherals like a second monitor and external hard drives. This is used when I'm not studying, so for stuff that requires me to use the laptop for extended periods. Much more comfortable having the screen at eye level.
I can't say I have a favorite place. I use it at my bed, my desk, floor, couch, hanging out with my roommates, etc.. Although, I enjoy using it the most in my room because I have my Airport express hooked up to my surround sound and computer speakers.