Keycol Hill indeed lies on the A2, though London-Dover traffic will use the parallel M2. Keycol does see a fair bit of traffic and there are a few local complaints about lorries, though the stretch between Sittingbourne and Rainham is very much semi-rural as the road hasn't really been developed since the M2 was constructed.
Location wise, you're about a mile or so from Sittingbourne and being close to the A249 you've easy access to the delights of the Isle of Sheppey now the new crossing's open and Maidstone's nine miles the other way.
Map here:
http://tinyurl.com/m6ltt