IAH, Terminal B - 3NOV10
I last had flown out of IAH Terminal B in the second week of October and noticed that they had finally erected plexiglas walls to enclose the security checkpoint (doing away with the old Tensabarrier). At that time, there were still 3 or 4 WTMD at the checkpoint.
When I flew out this past Wednesday, though, the checkpoint now consists of two WTMDs (one of which was reserved for handicap and special needs use only) and two MMW machines. Fortunately, once you get past the credential check, there are a couple of lane choices defined by Tensabarrier that you can choose to use one machine or the other up front. It is not made clear at that point, however, that you are choosing one machine or the other, you have to pay attention when using the checkpoint to see where your lane actually goes. I was able to avoid them by choosing wisely. I did not see any signage indicating the ability to opt-out where you would have been able to make that decision (i.e. immediately after the credential check).
CVG, Terminal 2 - 5NOV10
My return flight to Houston offered another opportunity to avoid the attack of the body scanners. The security checkpoint immediately behind the Continental/United/US Air check-in desks in Terminal 2 offers a single WTMD and a backscatter X-ray machine. I passed through this checkpoint early in the morning and it wasn't busy, so avoiding the NoS was a simple matter of lining up my stuff on the bag scanner line by the WTMD, though I did see some people going through the backscatter machine as I was putting my shoes back on. Again I noticed the lack of signage indicating the ability to opt-out.