I just got a full Ultegra Triple drivetrain upgrade (FD/RD/crank/chain/cassette/BB/shifters) on my Giant OCR and have been on a couple of rides so far with the new setup and it has made a huge difference for me so far.
My stock Truvativ crank was a 52/42/32 and the Ultegra is 52/39/30. I stayed the same on the cassette with a 12/25 but went with the 10 speed from the 8 speed.
I have noticed I mainly use the two largest chain rings now and only sparingly going up larger hills is when I use the smallest chain ring. I already feel like a better rider because of it. I still have a long way to go but I get happier with it every day.
Weight-wise I dropped about 1.3 lbs but was disappointed because I thought it would be a larger decrease than that after looking at a few different websites on component weights. Overall I am very happy with the upgrade and now my goal is to just keep on riding!