We (Mrs. Wrecker and myself) were going to switch to Vonage from Verizon a few months ago. But instead decided to cancel our landline altogether and just use our cells.
We sprang for the RAZR V3 which gets kick ass reception, then my wife promptly dropped hers in the bathtub (pwned).
Twofold Moral: 1) A good cell phone CAN replace your landline and more than likely be cheaper. 2) Don't drop your cell phone in the tub.