If your going to game, I don't believe a laptop will be optimal for you. If its for work, thats different..
I thought that gaming on a laptop would be fun once.. bad, bad idea. I went out and spent big money on an ASUS gaming laptop..
You need a mouse unless you can deal with playing with the touchpad.
You need headphones unless the speakers are great, or you don't want to talk through a crappy mic.
You can't really upgrade a laptop.. it is what it is for the most part.
The keys are more compact, and so you'll miss your full sized keyboard.
Has to do with the smaller keyboard.. but due to the size of the keyboard, your arms will usually bend IN and OVER.. which becomes uncomfortable on your wrists.
Extra cables due to the extra devices..
Limited USB ports.
Just my two cents.. get a desktop if gaming is priority.