This *will* work on TWC, however your local CSR will know absolutely nothing about how to get it to work.
I've owned one for over a year and have used it quite successfully to help keep my Time Warner Cable bill down in a 3 TV household. It's actually pretty foolproof once you get it up and running. It's the getting it up and running that's full of fools.
If you're on TWC, when you call your rep tell them you need a cable card *AND* digital tuning adapter. If you call and tell them what you're using and ask them how to get it to work they'll only send you cable card and then when you try to activate you'll get nothing and the 2 reps in the activation center who actually know what they're doing will spend hours trying to figure out the problem until they realize you don't have all the hardware you need.
The tuning adapter is the size of a cable box and adds a jumble of wires as the cable comes into the tuning adapter, back out to the HD HomeRun, and then also has a USB cable that goes from itself to the HDHR. Two power cables, plus the ethernet cable from the HDHR and you see how things quickly get messy. Find a place to hide it, but make sure you plug it into a power strip so you can reboot it the first few times you have to mess with it all.
I have mine fed into a net-top computer I use as a home server running Windows 7 with media center. Everything is hard-wired in my house via cat6, so I have 2 xbox (one for me, one for my BIL who was living with us) set up as media center extenders. What is the plural of xbox anyway? Xboxes? Xbii? That's 2 cable boxes I don't have to pay a monthly fee for, and it saves even more money as you can set any show to record via the xbox to the net-top (I have a 2tb drive hooked up) so I don't have to pay for extra DVR boxes or "whole home" DVR.
I envisioned game systems on all 3 TV's and no cable boxes at all, but realized that's too much to ask of the wife, and I'd never get to play whatever I hooked up to the main TV. I can also tap into it via the wireless on my laptop anywhere in the house should I want to watch hockey in the living room while the woman watches Criminal Minds on the actual cable box.