I have a mixture of 105,Ultegra and one piece of Tiagra, it works fine, i noticed the ultegra RD is a bit smoother than the Tiagra FD BUT would i upgrade my FD, hell no. My next bike I will be buying Ultegra but I don't see the point in going Dura-Ace if your not full blown competing. The only way I'm upgrading my gruppo on this bike is if I start riding with a group that rides all doubles, right now I'm rolling solo mostly and with some ppl who ride triples.