It's still a mistake to rent a cable modem
Although buying a modem requires a higher up-front cost, it pays for itself in a couple years. Here are a few things that have changed in the cable-Internet business. USA TODAY
The basics, however, have not changed: You should not pay a monthly fee to rent a modem unless you’re likely to move to a different cable operator’s territory in less than a year.
In pretty much every other scenario, you should buy the modem -- unlike cable boxes, there’s a functioning standard called DOCSIS (“Data Over Cable Service Interface Specification”) that lets you bring your own hardware. With modem prices generally under $100, the payback period can come in less than a year, depending on how much your operator charges to rent one:
You should, however, make sure you’re using a modem approved by your cable operator (see Comcast, TWC, Cablevision, Charter, and Cox’s endorsements), and you should also verify that it supports “telephony” if you get phone service from your cable operator.
But even with all of these well-documented reasons to buy a cable modem, cable operators continue to tell me that most subscribers continue to lease. At Comcast, for instance, a full 74% of them were paying rent on its current hardware as of the fourth quarter of last year.