I recently got my first compact setup on my new bike. I never realized how much I suffered on climbs with a 39-25; I always dealt with it at about 40 rpms up the steepest pitches. With 34-30, I can almost always maintain 80.
My new crank arms are 175, and I've always used 172.5. Initially, I didn't think I could use the 175s, so I picked up another setup with 172.5. I thought it was advertised as a compact, but it's 52/36. As it turns out, I don't really notice the longer arms, but I'm considering a swap of the arms/chain rings (As an added complication, I'm sending the crankset I'm sticking with to Pioneer to get a power meter installed).
My question after all this is whether to go with the compact or mid compact, as i have to commit to get the power meter installed. I live in the Pocono area, so there's a lot of climbing. I just don't know if there's a noticeable difference between the 34 and 36. I'm not concerned about the big ring.