i'll chime in with my two cents

I currently run Ultegra 6700 on one bike, Rival/Ultegra mix on one bike, and my wife runs 105/tiagra on her bike.

I am still getting used to the double tap shifting but I like it. I would say I like it better than the shimano style but its different. I dont mind either style of shifting. Both shift reliably and both get the job done. If setup right there shouldnt be any shifting problems. Heck I dont have any problems on my wife's 105/tiagra bike. I setup it up when she first got it and shes put 1000 miles on it w/ no need for any adjustments. The bike shop is not always the end all be all of adjustments. Theres always small differences once you put load on the system. It may shift fine while on the stand but very minor tweaks might need to be made during road testing. I agree the shop may get very close but in my experience it always needs some additonal adjustments. I dont have too much experience with many shops b/c I do all my wrenching myself. Only experience is with new bikes or friends of mine who had their bikes "tuned" up.

I have rival brakes and ultegra 6700 brakes. I like the modulation and feel of the ultegra better.

I cannot compare the front shifting. I like the front shifting on my Ultegra 6700 so much thats what I have on my sram bike. I also have a Ultegra chain and cassette. This combo I believe works out really well b/c it's quiet and has the front shifting that I really like.

Ergonomics are pretty close among the two. The Shimano has a thicker bottom end while the sram seems thinner all along the hoods. Both work great for my small hands.

In overall shifting there is a little more play on the shimano while the sram has more feel. This I think is by design due to the double tap system.

In conclusion this is just babble but I like them both. I have Ultegra on my race bike but mainly because I didnt want to swap parts. I wouldnt mind having sram parts on it either. I would go with whichever shifting style your more comfy with. They both work and work well. Also consider pricing. When on sale ive seen Ultegra 6700 go in the 700ish range on some websites. While I was shopping my Sram build best deal I could find of force was high 800s.

on a side note. 105 and Tiagra work perfectly fine if setup properly.
I didnt want to get into it but I had to comment on them because I've setup my wifes bike as well as a couple friends' bikes. Once they were setup they didnt really need any adjustment