OK, here's an update.
I *was* able to get simple capture from ATI AIW from *composite* in (no S-Video cables run to office yet) to work with Dscaler, using the Dscaler Alpha version 4.1.3, and the version 3 ATI Catalyst drivers for the AIW.
I spent a lot of time trying to get the capture from *tuner* to work, and while Dscaler can see the tuner, it does not seem to be able to adjust it. Dscaler could not scan and find any channels. It would, for some reason, show cable channel 4, but not any other channel.
And by the way, I wasn't getting any audio from composite or tuner, just video. But this may have something to do with the way the AIW is wired externally to the SB Audigy sound card.
This makes me hopeful that when 4.1.3 comes out, it may have full support for the ATI AIW cards. But I wouldn't make any purchases yet.
My new disclaimer: I'm a novice, just trying most of this for the first time. Please don't make any decisions based on my info until confirmed by more experienced sources.