I have two ATI all-in-wonder and found the Happauge (1998) infinitely better on teletext. As a TV they were much the same but I reckon the Happague was better on poor reception. The ATI does better on poor reception that my 500 quid panasonic VCR, video about the same but audio maintains down till the sgnal disappears on the ATI.
I have input and AVI'd & out from powerpoint on the older one which is fiddley if you exceed 600x800 because it refuses to output. The output to VCR must be at 50Hz and SVGA defalts to 751xsomething.
As for decoding cable/sattelite I have no idea, I haven't seen how you can do it PM me if you know how other unscrupulous square eyes do it. My sattelite is analogue (half an eye on the 1/2 inch disply waiting for the Rally prog.