I move around way too much, a laptop is a far more practical choice for me, not only so I can take it with me but also so when I go home for the holidays I can just stick it in a bag, slide it down the side of my carseat, and don't have to worry about damage.
It also does a perfectly good job as a gaming laptop, to the point where I simply don't get how people can say they svck for gaming. It's probably just the games I play, but I've never had a laptop related game issue.
I totally understand. I had to buy a laptop for work purposes and I managed to get one with a decent card for gaming as well. Ultimately it would have been cheaper to go with a desktop, but I needed the laptop for work-related travel.
There are a number of laptops that can deliver decent frame rates for recent games at 1920x1080. However unless you are buying used/refurb, you will probably end up spending at least $1200-1300 or so to get the cheapest among them, in other words with 1080p display and DX11 video cards at least comparable to the NVIDIA 460M or AMD 5830M, or better.
For the same price you can build a pretty powerful gaming desktop and have enough left over to buy a non-gaming laptop.
If you get a laptop with 1366x768 display, you will be able to get decent frame rates with weaker GPU, but IMO gaming on anything below 1600x900 you are missing out on a great deal of the visual experience of the game.