The Ithaca is super cool. If you like your 870's, you'll love the Ithaca.
It's lighter, smoother, classier, and feels faster than the 870. It has a similar crossbolt safety, and the slide release is in the same position on the front of the trigger guard. Except, it's correctly placed for a right handed shooter. If you're a righty, you can actually reach it with your trigger finger.
It also loads with the carrier up, so no pinched fingers or pinched gloves.
Older models will slamfire, meaning that if you hold the trigger while you pump it, it will fire as soon as it locks into battery. It's super fun for rattling shells off real quick, but demands excellent trigger discipline.
Bottom ejection is neat. You don't bean your buddies with ejected casings, and rounding up empties is as easy as dropping a shoebox at your feet.
I'm impressed with it. Disassembly is a pain, but other than that it's pretty great. A riot version is on my short list.