I think that what impressed me most about the SR-71 Blackbird, the first time that I saw one at Wright Patterson, was just how small they are... I thought that they'd be much larger.
Mark
I was most impressed the first time an A-12 flew into Kadena AB, even though I did not see it. I did observe the excitement in the Officer's Club stag bar. :-)
A casual observer would be hard put to tell the difference between an A-12 and an SR-71, but there are plenty of folks who believe the A-12 was the better plane and should have been kept.