I'm a neophyte with respect to vinyl / analog, but I've listened to 5 different cartridges in the past 6 months, on two different turntables, and I can say that it's definitely worth it to upgrade the cartridge, to the extent that you can benefit from it in your set up (how much resolution can your system reproduce?)
I've personally really enjoyed the Linn Krystal, the Koetsu Rosewood, the Koetsu Urushi Black, and the Lyra Atlas. In my limited experience, the Koetsu are very good tonally, but not the best with respect to detail; whereas the Linn and Lyra are very detail oriented.