You don't need 4 televisions. What if you would like to record 2 HD channels on your DVR while watching another. You cannot do it. Add to that 18Mbps is pathetic compared to 50Mbps and just because you don't use it doesn't mean others don't. If I could get 50/20 with no cap I'd jump on it way faster than 18Mbps which is comparable to Comcast's 16Mbps.
"Everything is relative." Just because you do use it doesn't mean others will. My wife and I simply don't watch that much television. In fact, if I could talk her out of the Food Network and HGTV, we would be an OTA only household. As for 18/1.5 Mbps for internet access, I'd take it over my 8/0.5 access that I have now for about the size cost per month. Can you get 50/20 with no cap?