What are the general thoughts on mixing groupsets? People seem to be very proprietary with their brands I am learning. I want to improve upon the stock wheels that came on my bike, and I keep getting recommended the Shimano Dura Ace 9000 C35. I have SRAM Red 22 groupset currently on my Cannondale Synapse Hi-Mod. Very pleased with SRAM, and if there was a brand loyalty, it would be there to some extent.

What are people's general opinions of this mixing and matching and what are "The Rules". I have just learned quickly as I get out and ride with groups everyone seems to have vocal opinions on everything visible on my bike.

Thanks