Well, it's also interesting to note that 12mbps is just not that much feasible with cable internet. And the further your distance is from your ISP, the lesser this speed gets. You can play around the 5-6mpbs spectrum, 12mbps is just theoritical at best.
Plus (although not related to speed anymore) the fact that security has always been something to consider when getting cable internet... mainly because of the nature of its "shared" infra.