Just to make sure that everyone is on the same page. Here is the back view of the STB:
You can see five (5!) coax cable connections there. The rightmost connection is what you use for digital OTA. This is your digital OTA tuner. (Yes, you can get all local stations, but only if they broadcast in digital.) It can only decode 8VSB-encoded signals. Most cable companies do not send 8VSB signals, though someone mentioned that certain cable companies might be passing 8VSB signals for local stations. (If that's the case, than there is a chance to get at least some channels from the cable, though I haven't seen any actual success stories so far...)
There is also a coax cable/antenna input on the left side and a coax output right under it. (I think this is what kawdog is referring to.) This is just a path-through connection. Whatever gets in gets out, except that VOOM inserts itself on channel 3. So, if you connect this coax output to a TV set, you can watch all your cable channels as usual, and you can also watch VOOM on channel 3. This works OK for SD TV sets, but not very helpful for HDTV, as the coax output is SD-only (480i). And even for SD, you still need to use two remotes: TV remote to switch to channel 3, and then VOOM remote to change VOOM channels. The only advantage of this coax output is that you can use your existing cable wiring to send the signal from the STB to another room and share one STB between two rooms. (You would need an RF remote though.)
The bottom line, you cannot easily integrate your cable within the STB. The best choice for you is to connect the cable directly to the TV set and connect VOOM STB via DVI or component cables. Yes, you will have to switch inputs, but fortunately this can be done with the INPUT button on the VOOM remote itself!