I was a Verizon FiOS Network Technician up to 2 months ago when I left the company. I was the guy who would fix network related problems or the one who CSAs would pass along a trouble ticket to when they couldn't fix your problem with the tools they had at their disposal. They really don't have much to work with and are on a 12.5 minute call average time limit. Unfortunately they will do whatever necessary to get the customer off the phone in order to maintain their call times, otherwise it affects their evaluations. That is the nature of the beast at Verizon call centers and is one reason I didn't want to be there anymore.
The FiOS TV & Internet service is truly superior to what the competitors offer at this time. The unlimited bandwidth available to the customer's house allows Internet speeds up to 50M up and down at this time and easily can be upgraded soon. Several markets are offering those speeds currently. The TV service has more HD channels than DirectTV or will soon. The telephone service is the one weak spot and that is when comparing to traditional copper lines that go back to the Central Office. Even cable companies have batteries around the neighborhood to provide backup power to your cable phone service, I experienced this problem when we had a hurricane 5 years ago and lost everything.
The FiOS service is passive and broadcast all the way to the house and the Optical Network Terminal attached to your house is a little computer that must be powered up to separate the three services from the optical signal coming to you. When a power loss occurs the backup battery is supposed to provide up to 8 hours of TELEPHONE backup time. The TV and Internet service shut themselves off to save power for your phone to operate in emergencies. It doesn't mean you can talk on it for that period of time, just be able to send/receive calls. The battery is a standard one you can buy at Radio Shack that is used for RC cars I believe.
Verizon is replacing all copper lines with optical over the coming years. If there is FiOS in your area you will be hard-pressed to order copper phone service through them. It can be done but there are special circumstances. The maintenance costs of the deteriorating copper lines and batteries at the Central Office is tremendous and that is what has driven the change to fiber.
Although I have Verizon Wireless phone service because of coverage and the IN NETWORK service I am not sure I would get FiOS for myself. This not because of the technology or reliability but because of the corporate culture that I experienced. Passing the buck and maltreatment of employees, not to mention how customers get treated because of internal processes makes Verizon one company I want to avoid. Keep in mind though I worked in a place where all I saw were customer problems, and they were the worst problems. Many people are perfectly satisfied and have never experienced anything to complain about.
I guess my point is FiOS is here to stay. It is in the growing stage at this point and technical problems will be ironed out. The biggest drawback to FiOS is the juggernaut of Verizon's culture and antiquated internal systems that make efficiency a dirty word.