Ken,
While I understand what you are saying, I think you miss the point of what he is saying. Sure, a peer-to-peer is good enough to run AC. And, desktop grade hardware will run it as well. And, you do better backups than most. But, what you are saying is a little like, "I have always used tires with less tread and done fine."
One thing that users I think misunderstand is that there is a big difference between Client/Server and Client/Server with a domain and Active Directory. The latter requires a good deal of knowledge in networking, especially DNS, and the management of users, etc. Granted in the end it makes everything easier. But, you can have Client/Server without the headaches of "running" a network or hiring an IT. You take your workgroup computer out and you insert a server quality computer. Then you run a workgroup. This gives you the benefit of having better hardware with RAID, etc. without the hassle. Then, if down the road, you wish to switch over to a domain, you simply attach the computers to the server in a domain fashion.
