Originally Posted by PugRider

I have an Ultegra 6503 FD on my Miyata Alumicross and it is without a doubt the best, most trouble-free FD I’ve had. In fact, when I’m riding that bike it’s the only time I’ve ever actually noticed what a good job the front derailleur does.

As others have said, however, it’s not completely mix-and-match; I’ve owned or worked on a lot of bikes, they can be finicky; you think you have everything figured out and when it gets clamped on it hits the chain stay in low gear, etc. Helps to have a few different cage shapes in the bins for trial-and-error.