I used to get dropped in cat 6 road races in the first few km but after installing the Shimano Ultegra 6700 Derailleur Pulley Set I set 25 KOM's on my first ride and instantly upgraded to UCI Pro Continental Status. Forget deep section aero wheels and skinsuits, with these jockey wheels I save so many watts I can effortlessly ride up hills at 67 WKg. The only downside is now that my rides are so fast and long I have to change tires twice because they wear out.
As with most things, you get what you pay for. I tried the aluminum pulleys you can find on Amazon. They were real pretty, but the pulley immediately began to pull off the bearing after they were installed. Any side load was not tolerated well at all. These Shimano pulleys, however, can take the side loading and perform great. No more no name pulleys for me.