Eric:
 
Per our conversation, I thought I'd fill you in on the results of my use of the Samsung DTV STB (SIR-T165).  Perhaps you will find this information useful.
 
The purpose of setting up the DTV STB was to determine if my current antenna setup is adequate for DTV reception, in preparation for a later purchase of an HDTV.  Hence, I used a small screen convenient to work on, not one of our larger TVs.
 
The STB is connected to an OTA antenna, the Channel Master 3010 STEALTHtenna (with the internal amplifier), rated to be a Large MultiDirectional.  This antenna is 15" by 52", chevron shaped and is mounted on a five foot mast on a townhouse roof two floors above ground level, with no rotator.  Total cost of the antenna, amp, mast, support, etc, was less than $100.
 
I have a HTPC.  To connect the STB, I simply disconnected the composite, audio and S-video connectors from my DISH satellite receiver and plugged them into the back of the STB.  The cables lead to an ATI 7500 All-In-Wonder video card installed in the PC.  The standard ATI software was used to drive the display, a Sony 21" (19" displayed) 4x3 CRT monitor.  This small setup is used in our master bedroom.  The applicable rear switch was set to analog.  Nothing could be simpler.  With this setup, I could switch between the composite, s-video and satellite (NTSC only, via coax) inputs using the PC software.
 
With all equipment on, I set the STB to memorize (automatically scan and store all receivable channels).  It found all the analog channels we are accustomed to receiving, including those from Baltimore.  It also found 9 "channel groups" of digital channels- 21 actual digital channels in all.  I must point out that it found one group, 75, consisting of channels 75-1 and 75-2, that are not listed on antennaweb.  This group mimics the channel 50 group.  All DTV channels were received indicating medium strength signals on the STB, except for the channel 57 group, which was a bit lower than medium- yet all produced perfect video.  All currently active digital channels for this area, as listed by antennaweb, were found by the STB except for channels 20.1 (WDCA in DC on freq 35) and 66.1 (WPXW in Manassas on freq 43).  As WDCA is directly in line with the aim point of the antenna and is a nearby station, I believe this station is not actually transmitting digitally at this time.  The other station, WPXW, is off axis to the aim of the antenna (which is a multidirectional) and is located some distance away.  The analog counterpart of this station, channel 66, is received weakly here, so the digital station may be transmitting at a low power level, if at all.  Since this is a PAX affiliate, and we already receive PAX via satellite, there is no need for a rotator.
 
With the STB set to display widescreen transmissions in letterbox, some 4x3 analog programs retransmitted on a DTV channel as 4x3, are displayed in a box on the screen on the DTV channel, surrounded by grey and black bars.  Others are displayed full screen.  At first, I thought this was station dependent, but the behavior is inconsistent.  The same station sometimes appears boxed in, sometimes not. The "boxed" screens can be forced to full screen by the changing the STB to display widescreen transmissions as full screen, but then this cuts off the edges of true widescreen programs.  Whether this is caused by the broadcasters or the STB, I don't know.  Since the 4x3 analog programs retransmitted on DTV stations as widescreen do not have this problem, and certain stations were never observed to have this problem, I suspect it is a station controlled situation.  The STB does indicate HD sometimes for non-HD 4x3 programs.  The box never froze up, never locked on one channel and refused to move.  So either all PSIP data was perfect (doubtful) or this problem no longer exists for this model.
 
Even on such a small screen, the digital programs were unquestionably better than their analog counterparts.  They appeared sharper and had brighter colors.  Although most DTV stations are transmitting the same program as their analog counterpart, and in SD not HD, there was still a noticeable improvement.  And enough widescreen HDTV was available to note that these were impressive, and with no pixilation.
 
To continue the test, I unplugged the monitor from the PC video card and plugged it into the DB15 on the back of the STB.  No other adjustments were made, the monitor did any such adjustments invisibly.  It just worked.
 
In case this information may be useful to you, I list the stations received below.  The analog stations are listed, followed by any applicable digital station (number dash number).  Some digital stations have no analog counterpart, and some only broadcast a fixed message:
 
2     ABC     Baltimore
4     NBC     DC                4-1
5     Fox      DC                5-1
7     ABC     DC                7-1     7-2
9     CBS     DC                9-1
11    NBC     Baltimore
13    CBS     Baltimore
14    TFA     Arlington
20    UPN     DC
22    PBS     Annapolis
24    UPN     Baltimore
26    PBS     DC              26-1    26-2    26-3    26-4
       UNI/IND Goldvein      30-1    30-2    30-3    30-4
32    PBS     DC
45    Fox     Baltimore
50    WB     DC                50-1    50-2
54    WB     Baltimore
56    IND     Fairfax           57-1    57-2    57-3    57-4   (yes, 56 and 57)
66    PAX    Manassas    
       WB                          75-1    75-2     mirrors 50-1  50-2
 
In short, for my area at least, DTV is alive and well and ready to be a full time replacement for the old broadcast analog NTSC signals.
 
BTW, I found you as a rental source from the AVS forum.  You were mentioned under a thread for the DC area. If someone rents this in the future that plans to connect it directly to a computer monitor via the DB15, it produces absolutely smashing images set to analog and 1080 or 720.  There is no need to leave the setting at 480i unless they run it thru a PC video card first.