I got my Zoom 5510 DSL modem today. I'm testing cheap equipment for DSL connections, since cost is a big issue to some of my customers. I'm happy to say it does indeed work on linux with decent support, though the firmware was a little hard to find.
I'm looking forward to playing with the non-PPP parts of the ATM stack to see if this could solve the expensive problem of terminating VoIP reliably. With a willing telco interconnect, and ATM as far as the home over DSL, I can see it being very attractive.