What sort of connection speeds would ISDN give me?

Unlike analogue 33.6k/56k modems, ISDN modems do not connect at different speeds. Either an ISDN modem connects or it doesn't. ISDN modems do not negotiate to get the highest speed, they will always connect at the speed that they are set to connect and they will do so almost instantly compared to regular modems.

Most all ISDN modems are set to connect at 64kbps per channel (remember that an ISDN line has two channels) so when you dial and connect to AOL, it will always be at 64kbps unless you have your ISDN modem set to 56kbps.

With ISDN it is possible to combine two channels together to get a transfer speed of 128kbps, known as bonding. However, this is a more expensive option and at the moment AOL does not support bonding.