Disclaimer: I do not own a converter box, so I cannot speak specifically to the performance of any individual box. But...
As several posters have pointed out, not all boxes are HD capable. HDTV is a subset of the larger digital TV picture and all of the tuners inside of any converter box should be able to tune an HD ATSC over-the-air signal, but not all have HD "outboard". Once the signal is tuned, the resulting signal is rasterized by a GPU which may or not be capable of passing an HD signal to the television set. Or the manufacturer may have chosen to disable that feature to save money on the "spigots" on the back of the box.
Also, perhaps not as clear, but also mentioned by several posters, is that tuner quality/performance varies. Utilizing the same antennae, some converter boxers may not be able to tune as many channels as others. A US-based tuner manufacturer, Microtune, has filed comments with the NTIA.
Microtune says based on their private testing of converter boxes approved as part of the federal coupon program, they allege that converter boxes that do not contain Microtune tuners do not meet the performance requirements that the boxes are legally obligated to meet. (reading between the lines: there are government subsidized boxes with poorly designed, cheap, rushed-to-market, overseas chips)
The Community Broadcasters Association
is also taking action against
the converter box coupon program. Contrary to popular belief, and a PR campaign that oversimplifies the DTV transition, only 20% of the nation's TV stations will cease broadcasting in analog next year. Up to 80% of the stations in the US will continue to broadcast analog after it "goes dark". These stations are classified as Class A (lower power meeting certain broadcast standards), LPTV (low power), and translator stations (used to relay signals to remote areas or over mountainous terrain). They are not required to transition yet, and Congress/FCC have not yet set a date for their transition. Most of these stations have not been assigned channels by the FCC for them to begin broadcasting in digital. The CBA objects to lack of analog tuning capability in these boxes, which they allege is a violation of the "All Channel Receiver Act".
Further, heavily anticipated boxes, such as the one produced by Echostar, will fair to reach retail channels before the first converter box coupons that are being issued will expire. The public does not appear to have a firm grasp on the TV transition, with most understanding that analog TV will end in February (which is factually incorrect), but not understanding what that actually means to them (or even if it will impact them personally).
Obviously, those with cable will be unaffected. But over-the-air TV serves for more than just entertainment. Over-the-air (OTA) TV serves small communities, minorities, low-income earners, those living in areas without cables, and foreign-language speakers. And these are the people least likely to understand the transition, which ironically, being the ones most affected by it.
The real benefit to having a strong OTA industry across this country is for national security. OTA TV can still be broadcasting when the cable and power is out. And, in the unfortunate scenario that our homeland is a warzone, OTA TV towers can move and be more rapidly rebuilt after destruction. OTA TV serves as a critical part of our nation's emergency preparedness - whether tornado or terrorist.
It looks like a lot of people aren't ready for DTV - and not all of them are viewers.
Personally, I watch OTA TV and don't waste my money on cable (you can watch South Park and The Daily Show online for free and Netflix fills in the gaps). But I still haven't figured out which converter box is for me. I'm not sure that the coupons offered in the NTIA program cover any converter boxes that I really want to get.