glen,
If you cook different types of rice (i.e. sushi / sweet / porridge / brown) or keep your rice around for >12 hours then yes, they are worth it.
If you just want a solid, reliable rice cooker go with Tiger or Zojirushi. Both are kind of pricey but definitely worth the extra dough if you enjoy your rice.
Jzero - I'm assuming you're not even remotely Asian otherwise you'd understand the sheer necessity of having a rice cooker in one's home. I'm sure my fellow Asian ATOT'ers will agree wholeheartedly.
Whitewonder - Fuzzy Logic rice cookers cook rice differently depending on various conditions / rice type so you ALWAYS end up with the perfect pot of rice. They also have the ability to turn on/off the heating element so your rice doesn't dry out if you leave it on for a while.