Many excellent maps contain stairs, but they can have a subtle effect on game play that you may not intend.

There are two ways to make stairs, each with their own advantages. The first way is to create a series of brushes, one for each stair. The most known drawback to "real" stairs is that they create more wpolys on screen. The advantage is that they look great. The other common way to is to make one brush in the shape of a ramp, and then use a texture to make it look stair-like. This reduces wpolys but doesn't look as nice.

But there is a very important game play element to stairs that is often overlooked. Load up a Counter-Strike map with "real" stairs in it. Purchase an m4a1 or ak47. Now run up the stairs. notice that the size of your targeting reticle does not change. Now run down the stairs. See how the reticle rapidly changes size? This is because of the game physics. When you are going up the stairs, the game does not penalize you. However, going down the stairs, you are literally falling from stair to stair, and take the falling accuracy penalty.

This can be used by mappers to their advantage. If you have a staircase area in your map when both teams are frequently running towards each other while on the stairs, the team at the bottom will have a slight advantage. If this is not what you intended for this area, you could try using a ramp instead.

I know this is a very minor point, since in most cases the height and camping advantage of being at the top of the stairs is far greater, but there are a few map designs where long stairwells become fighting grounds.