I went from 105 to Rival...I will never go back to Shimano. It never felt 2nd nature to me, even after riding 3500 miles. SRAM isn't as quiet, but I have dealt with a LOT less hesitation and only one dropped chain in over 2300 miles. My 105 was notorious for just randomly dropping--not even while shifting (I'm sure this is in part to having been a triple--my SRAM set-up is a compact double). No one could ever find anything "wrong" with it, it was just flaky.

SRAM is just is more intuitive for me, too. On my 105 I was forever shifting in the wrong direction.