I've got DOCSIS 3.0. I had to call Cablevision and request a new modem, but they didn't really give me a hard time.
I couldn't hit my 15Mbit downstream cap with DOCSIS 2.0, due to congestion. Not a problem at all anymore with 4 bonded downstream channels and DOCSIS 3.0
Cablevision doesnt mind everybody having docsis 3. Also the cap is now 22 down .
I had 22mbs down with CV, but with recently renegotiated deal CV added "boost" - "promised" 50/5 for $15 - end result - $6 more a month I get ACTUAL speeds - 65/8 with new DS3 modem