At a previous house we did not subscribe to the Verizon TV and connected our router directly to the ONT. This was the most painless Internet service I have encountered. Prior to removing the Verizon Gateway I had regular issues.

Recently Verizon has started using a new Gateway for their Gigabit service and I don't have any significant experience with this unit -- other than I haven't received any calls for the first few weeks.

As lippavisual points out, if you use the FIOS TV service, the cable boxes need the Gateway for Meta data. Also, if the FIOS Gateway is not in front, Verizon tech support will become very crabby because they will not have direct access to data logged by the Gateway.