Let me tell you it sucks living in the same room you grow in! But it can be done, and I would do it again if necessary.
First off you got the buzzing sound of the ballast (mine was 1000w) it is the most annoying sound in the world durring your veg cycle, you try to set the timers on/off at reasonable times. But you try to sleep in on your day off, after a night of heavy drinkin, and you have to wake up to an annoying buzzing sound!
Then theres heat issues. I was living in the redwoods so the temp outside was always above 32f, and below 75f year round. My room with the light on was anywhere from 70-85f, so if you live in a warmer climate this could pose as a huge problem around summer.
And the biggest problem is security!!! When your trying to grow pot in a small ass room, it gets really hard to keep people from finding out. Close friends family, you dont have to worry about much about. But people that come over for this, that, whatever, people you dont know too well, they can smell it, or notice an eerie light shine from under the crack of the door (HPS, and MH have a distinct color of light), or hear the ballast buzzing and fans, this can create a severe security risk.
All the problems addressed, the knowlege of indoor gardening, being able to frequently admire the beautiful plants you grew, smoking it up, and the fresh oxygen in the air, make it all worth while in the end I think.