And here's me thinking this was a new thread! Imagine my shock when I read something I wrote back in June and I still actually believe it!
Anyway, I ride a sloping top tubed 62cm equivalent steel road bike, and I've never experienced 'shimmy' even at 55mph. In fact, my bike feels like it's standing still at high speed - it's very stable and intuitive. I attribute this largely to the geometry of the whole package - 48mm raked fork with a 73deg head angle ( 51.9 trail ), and a 71.5deg seat angle, 425mm stays and a long wheelbase.
This current obsession with short and steep bikes sure doesn't help - especially when most manufacturers spec a 45mm raked fork with a myriad of head angles throughout a model range....some bikes will handle okay while others will feel like *****. Welcome to the world of 'Mass production' I guess.