I must chime in here that the "jump on an open network" worked for me for quite a while, as well. But I got my own, also RCN, internets-only (I have no need for cable, and my cell is thru Verizon). I have found it fast, reliable, and now possibly cheaper than I thought since I didn't realize I could try to get my discounted rate back!
Another fan of RCN , all things considered