The cables that Cablevision supplies are not particularly good. They're more like 3 thin audio cables than the 3 thick video cables that they should be.
Most of my friends who have Cablevision HD have upgraded. However, if you decide to upgrade, don't pay the inflated price for Monster Cable. Go to Best Buy and get the Acoustic Research Component cables (~$25 for 6ft, ~$40 for 12ft). They are just as good as the Monster Cables for less than 1/2 the price.