INSIGHT LINE-UP ON THE HD CONVERTER BOX
012 - C-SPAN (why is this here?)
750 - HBO HD
751 - Showtime HD
760 - WKRC (CBS)
761 - WLWT (NBC)
762 - WCPO (ABC)
763 - *
764 - KET1
765 - KET2
766 - KET3
767 - KET4 (Annenburg)
768 - CET
769 - CET (HD) (only on occasionally)
770 - CET (PBS kids)
771 - CET (PBS you)
772 - CET Plus
774 - Bravo HD+
775 - ESPN HD
776 - Discovery HD Theater
777 - HD Net
778 - HD Net Movies
COST
Currrent subscribers can get all this (except HBO and Showtime) for an additional $17.90 per month [UPDATE]: digital box ($7.95), HD box ($2.00) and HD Pack (channels 774-778 for $7.95).

To get the HBO HD and ShowtimeHD version you need to subscribe to the respective non-HD channel packs at ~$10 each (and pay for the digital box). Insight claims that you only get Bravo HD if you have the normal Bravo channel, but the HD channel comes through regardless.
If you are not a subscriber, basic service is 26 channels at $13.50 + taxes. I subscribe to their classic service (69 channels at $39/mo. + taxes). Taxes are ~$3.
Don't forget the one-time HD installation fee ~$40.
CONVERTER BOXES
They make you take the digital box ($7.95/mo.), but all it gives you is the channel guide, digital music channels 500-534 and their interactive services. The digital box has nothing to do with HD. The incoming cable signal gets split to each box (digital and HD), and each has its separate output to your TV. They refuse to let you have just the HD box ($2.00), citing that their plan is to go to a unified box that will cost $9.95, so you have to take and pay for both boxes [UPDATE].
CABLE AMP
If your signal is split too many times, you may need a cable amp. Insight uses the Electroline models because they can also send a return signal needed for HD. They charge $40 + installation fee. I bought an Electroline EDA 2400 (4 outputs) on ebay and installed it myself.
