Certainly not what you're after but one of the nicest riding bikes I've had has been a Motobecane Super Mirage with Columbus 'inexternal' tubing, of which it's hard to find much info about. A mid-end bike, it's no doubt largely due to the geometry (fit me perfectly) but it certainly rode nicely, not too heavy, no noticable flex and it just did everything it ought to really, really well, cornered, accelerated, long journeys, it did everything comfortably and confidently
Sadly I sold it to a friend who needed a bike, but if all goes well I'll have the same model, same size, a few years younger (MBK), and far far pinker (90s) some time this weekend. I'm more excited about picking this up than any other bike in a loooong time.