What impresses me is that after 30 years her "Bart" voice still sounds exactly the same. Voice actors don't get enough respect, IMO, and she's one of the best.
She has an extensive resume beyond The Simpsons, too - but most of them are titles you and I might not be familiar with unless you have young children (e.g. "Rugrats", "Lilo and Stitch" and the video game "102 Dalmations: Puppies to the Rescue!").
If you're interested in voice actors, check out the documentary "I Know That Voice". Ms. Cartwright makes an appearance, as well as many (sadly, not all) of your other favorite cartoon voices. The film was initiated by, and is hosted by, John DiMaggio, who we all know as the lovable delinquent robot "Bender".