so, i took my bike to a different LBS today. the primary mechanic wasn't in, but the guy i spoke with (who also rides a cross bike w/ same front gearing -36/46 - and same sram rival FD) took it for a spin and said it seemed to be working fine. he also commented that he believed all FDs are antiquated and none work perfectly. he then allowed me to take his bike out for a spin and i experienced similar difficulty. which, some of you are already thinking, lead me to believe that...the problem was me. mechanic said i need to take pressure of pedals when shifting FD, which definitely makes a difference. he also pointed out that i might need to hold the shifter in for a few rotations to ensure the chain catches on the ramps - which didn't make much difference for me.

however, i have a difficult time believing it's entirely me because the FD shifted fine, overall, for the past 600 miles. so frustrating.

in response to some of your comments:

i've spoken to a couple people & the sram rival FD should work fine with 36/46 gearing.

FD cage is directly above the outer chainring - practically touching. haven't tried bending cage - not sure i wanna mess with that yet.

chain measures exactly 12" from pin to pin.

incidentally, neither mechanic believed it was a problem with the FD.

thanks again!