Been using a 1.2GHz for about a week and a half while my 1.3 was on a long wait - it showed up earlier than expected a couple days ago and been using the 1.3 now. Tons of posts about benchmarks between the two seemed to show a 10% boost (given specs, that seems that it's pretty consistent with you'd expect). Perhaps there's some "justification bias" in this, but I have both machines sitting in front of me and still in return period on both and would actually rather like to save the $ between the two, but I am keeping the 1.3. The 1.3GHz *seems* faster and more efficient (again, plenty of threads about the benchmarks one can analyze and tear apart and quantify, these are qualitative findings from an n of one: me). Builds in Xcode finish faster (no, haven't and not going to pull out a stopwatch), machine runs cooler on the same workload (no, no thermometer), and seeing about 45mins better battery life on my day to day tasks (mix of email, web [using Safari exclusively, as much as I loathe it, it's a great power optimized browser, and Chrome isn't], Xcode, Google Sheets, and Keynote). My impression is that Intel's "hurry up and get to idle so things can cool down and go into uber lower power state modes" philosophy is working in the favor of my workload more so with the 1.3 than with the 1.2. The 100MHz clock diff at idle isn't that big a diff, but 300MHz at peak is a bit more a difference in absolute #s. I wonder if AAPL got their own bin of 5Y71s for the 1.3GHz chips they're speccing on these machines as they're PN-wise identical so the 1.2GHz 5Y71s (I see conflicting information on whether the 1.2 is a 5Y71 or a 5Y51, though)...if they're both 5Y71s and they're just sub-binned we'll probably never know, but maybe there's a sub-bin for chips Intel sells them that bin even higher with more favorable thermal characteristics, etc that AAPL is clocking at the 1.3/2.9 spec for the 1.3s? Anyway, wanted to keep the 1.2 and saw the $$$, but the 1.3 and the modest $$$ diff compels me to return the 1.2, even if it's a fluke and I just have a better battery on it? Totally unscientific data points here, but plenty of GB benchmarks posted for those that want those, just my observations between the exact same work/setup/user in a 1.2 vs a 1.3.