I like your idea of the large simultanious (bi-directional) transfer across the HDSL.

I agree that HDSL at minimum, is equally as reliable as a regular 4-wire T1. Now that I think of it, Bryan brings up a great point that HDSLs are either UP, or their DOWN.

I'd like to share a quick follow-on point about ADSL Service: Here locally, ADSL is a DSL service that is assigned to an ordinary POTS line. The POTS line is assigned no differently in the switch, with exception that the pair passes thru an ADSL shelf prior to leaving the CO.