don't know what the argument is about
We're a small business needing call queueing, tranferring, voicemail, multiple lines and out of hours messaging.
VOIP wins hands down from a cost point of view
We've got a Zen 8Mb ADSL line (why use any other ISP???), QOS sorted on our router and dedicated Snom phones connected to an Asterisk server on our LAN. We use Voipfone as our provider and are dead pleased with them.
Call quality is better than POTS, way way way cheaper as we only have 1 line (we can typically have 3 calls on the go), and I've been pleased with uptime; a quick look at the logs shows that in the klast 2 weeks we have had 100% uptime.
Our router has a 3G backup link too, so even if the local BT exchange goes phut (as it did last year for 3 days) we've got comms PLUS even if everything blows up/ burns down Voipfone give us autofailover to any number we want.
For SME VOIP is the way forward- cost effective and good quality.