Man, are cable manufacturers like these desperate to stay in business! Most of this stuff they come up with could be considered little more than high priced snake oil. Yes, there needs to be some signal boosting due to HDMI's poorer performance over longer lengths, but one would think you'd want to make sure the signal was strong and error free at the source and at the display. And I doubt it needs to cost as much as many cable companies like to sell these boosters for.
To say that, generally speaking, HDMI overall is a poorly designed interconnect concept would be an understatement.