When I placed my order for SDSL I was asked how many PCs would be connected, etc bacause I asked for extra IPs. I had no problem stating that I intended to build a network and would have a router plus a linux firewall, a server running several services including apache, sendmail, Mailman, BIND, ftp and others, and would have at least two workstations. This is all so that I can learn network administration, Linux and other OS's. DO expect that if there is an outage it will be corrected quickly. Customers are the reason for the ISP's existence.
Customer support is critical.
Residential customers have the same expectations as business customers when it comes to connectivity and DSL is no different to many of us than voice service. If it is down, it is in many cases more than just an irritant. To me, it is as important as electricity service. Whether a customer has one or three PC's and a router on the connection should make no difference. The provider should be upgrading as connections are ordered if necessary.