Channel surfing is slow for ANY hookup you use with the Replay. As far as digital cable boxes -- it just requires some tweeking to get it to work well...
Posts have been made about GE and Scientific Atlanta boxes. I've posted MANY times on this subject (maybe I should make a mini-faq on digital cable). By tweeking my system I went from 10+ second channel changes to <2 seconds.
To make it work well:
Assuming your box has 1000 channels, you will change channels MUCH faster if you add an "8" in front of the device code. A "6" forces 2 digits to be sent (as in enter '5', send '05'; an "8" forces 3 digits to be sent (as in '5' sends '005'. You also want to force an "enter". Because the lower channels (that you would get without digital cable) are analog, they take longer to tune than the upper digital channels. It may be easier on your eyes to slightly lengthen the black screen "delay" time the Replay unit uses. I compromise -- my delay is a little long on the upper channels, a little short on the lower channels. Instructions on how to do this are in the FAQ at the top of the page.
On Digital Cable Audio/video:
Your box will probably have an S-video and Composite video output. The sound will be composite l/r and dolby digtal AC3.
Forget about the digital audio.... you ONLY get it fot the "digital" channels (not the analog ones), and it is ONLY DD 2.0 (NOT DVD style DD 5.1) -- when you decode it through a dolby digital receiver, with pro-logic, you will get the same 4 channels of audio you get if you send the r/l composite audio through a dolby pro-logic receiver. No gain here. Plus, Replay can't use dolby digital. Only buy a dolby digital receiver if you have a DVD player.
To get the most flexibility:
If you have a strong signal, split the cable at the wall. Hook the RF up to the Replay box and the digital box. Send the S-video output and composite audio to the Replay from the box. If you have an A/V receiver, split the composite audio between the Replay and the A/V receiver, and send the composite video to the receiver. If you have a REAL strong signal, you can split the RF cable THREE ways and input it into the TV's rf input. Compare the split/not split video picture to see if the signal degrades -- if it doesn't before/after, your signal is strong enough.
with this setup, you can:
Record on the Replay from the analog cable while watching the digital box (through the A/V receiver) on your TV
Record on the Replay from the digital cable while watching the RF analog cable on the TV