I currently have an older airport extreme and am considering upgrading to the new airport extreme. Is it worth it?

Do you have any wireless client that support 802.11ac? Yes, then maybe an upgrade is in order, especially if you have either an 802.11g or 1st/2nd generation 802.11n AirPort Extreme. If not, then I would suggest that you only need to update if your wireless network clients would benefit. That is, getting a new 802.11ac base station will NOT make your wireless network any faster for 802.11g clients.

Great! Then upgrading to an 802.11ac AirPort base station, should offer better bandwidth performance for you new devices. Again, especially if you have either an 802.11g or one of the first two generations of the 802.11n Extremes. Besides, if it doesn't work out, Apple does have a return policy.

Yes! I just installed one and it extended the range enough to reach parts of the house that were off line before.