we tried switching to att voip several months ago... but the switchover was a pain in the ass. att wasnt able to redirect all calls to voip... so we would recieve 1/2 on the landline, and 1/2 on voip. went vack to verizon for a few months.

end of last year, we switched to Vonage. Setup was a breeze, they gave us a temporary number and forwarded all out calls to that line for 2-3 days until our number was fully switched.

i really dont notice a difference between voip and a pots line. the voip unit/router has QoS so heavy downloading wont affect voice quality.