Well, there's a difference between what you guys are talking about and what was just asked about. A platformer has much
different requirements for generating rooms than games like Diablo or what was described by Kevglass (Which seemed to be more about room definition for a dungeon, than anything).
However, enemy placement is very
important. If you haven't, watch what's linked to here http://www.java-gaming.org/topics/sequelitis/25713/view.html
. The first, then the second, videos. Basically, randomly placed enemies are less interesting or fun than intelligently placed enemies. They're a lot
more frustrating and difficult to deal with. Especially when you get enemies spawning in a way that their typical weakness is completely removed (Like, say an enemy that you're supposed to be able to attack from beneath spawning where you can't do that).