I use my AIW and I have digital cable. The tuner for the AIW cards is like your VCR's tuner, it will tune in the analog channels, but you need to use the digital cable decoder to tune digital cable channels. I hook the digital cable decoder to my AIW via composite video-in, and the analog cable to my AIW tuner. Switch the input in the ATI TV application to watch digital cable (change channels with the decoder's remote) and switch the input to use the AIW's tuner to watch regular analog cable. Works great.
Also, The IQ is excellent from the digital cable, and I've recorded several movies that I've encoded to CDR. You can use the scheduler to record unattended, not as flexable as guide plus, but somehow I've managed over the last couple years to have never used guide plus to record a show.