Drow is one of the MOST potent carries in the game. If left unchecked, she can out DPS any other carry by mid game.

Don't underestimate the power of her silence. This can be a HUGE life saver / crowd controller. Chase people down with Frost arrows and make good use of map awareness. She does not have ANY kind of escape, so if you see yourself getting ganked more than once within a few minutes, bypass treads and go for Phase boots.