Bonded Pipes

Does anyone out there have any comment on some of the new, bonded pipe products like the WebRamp M3 or Transendmodem? From what I understand they are saying that multiple lines can be aggregated to act as one, virtual line. My question is: will the ISPs support multiple sessions from the same account (name/password) without charging N X the number of lines per hour? If yes, then these like like cheap alternatives to ISDN. If not, is there any benefit to aggregating?