I had no trouble when I went to Shimano from my mountain bike trigger shifters. It was totally intuitive and I never made any horrible errors. However, given my poor track record with even the most minute mechanical change, I decided against SRAM for my custom bike, despite the LBS pushing me for this. I am small and I have short arms and smaller hands, but I think my fingers are actually long for someone of my size. Anyway, I've never felt the hoods on my bike with Ultegra are too big. For me, the biggest thing that helped me was finding a bar with a short and shallow shape, along with the short reach brifters. Since Shimano no longer makes the short reach brifters in Ultegra, I went with 105s on the custom build, but the reach is about 2mm longer in the drops than on my other bike. I rarely use the drops anyway, but I doubt SRAM would make a difference. I think I made the right choice, because just getting used to a more relaxed geometry, the compact, and new pedals was enough. I was a wreck for 6 months.
My friend has a Ruby with the same compact double set up (mountain gears on the back), but with SRAM, as I have on my custom bike, with Shimano. Since I am probably going to be upgrading the bike I will be using on our trip next summer to a Ruby (the company gives this option), I want to try her bike out, as we are the same size. However, because she has SRAM and the bike I will be renting has Shimano, I told her I will test it on the trainer, as I don't want to crash her gorgeous bike!