Yeah that's a good clip. I think that's from Mindenhall AFB. Others can correct me. She's a bit deceiving since she's such a large bird that is almost 110ft long. About half again as long as an F-14 or F-111. Dang big. And what gets lost on folks is that her speed performance is rather anemic at low altitudes where she can't take advantage of her turbo-ramjet capabilities. I don't have the speed curves in front of me, but I would be suprised if she was much more than Mach 1 capable at low altitudes with her J58 engines.
But she sure could sing at altitude with Mach 3.3 officially sanctioned and Mach 3.5-3.8 unofficially occurring. From all that I have read, the mach limit of this airplane was only kept in check by the shockwave generated by the airframe. Above Mach 3.5 it was claimed that the shockwave would "narrow" (as it compares to the airframe centerline) and had the likely potential to enter the engine inlet and unstart the engine. Not only was this a potential thrust loss, but a compression failure was deemed to be structurally high risk.
I have read a report from an SR-71 flight test that included increasing yaw tests. I'm not privy to the actual test results, but the test resulted in catastrophic airframe failure and the death of the RSO. The pilot survived only due to sheer luck. He did not eject, but was separated from his seat due to the extreme forces became concious at a lower altitude, only to have enough time to execute his chute. Severly injured, he was rescued by a farmer in a helicopter who witnessed his chute opening during a normal run around his ranch.