My wife has a i5 4GB 128 GB model now and I have an i7/8GB/256GB MBA - both from mid -2012 - bought off the refurb store. We are both happy with the performance - both machines are blazingly fast with no lag whatsoever. I bought the i7 because I am a scientist and also like to have every program on the computer open. Wanted to summarize my experience so far for others. The i7 can handle having everything I have open easily - I run scientific computation programs like MATLAB and python but also have safari, chrome and every icloud application running now. Also, Papers2. I think the i5 can handle most of this too, perhaps with some minor trouble due to memory.. but I prefer my i7. Both machines are always reasonably cool to the touch under any load. Under max load, they are definitely warm in parts but would be comfortable even on your bare genitalia if you are the kind who does that. Battery life seems decent on both though we need more time to decide on that - > 6 - 7 hours for now. The main problem with the i7: 1. Sudden rapid climbs of core temperature to 100 C when I throw a difficult task at it - followed by equally rapid drops within 2 seconds to 50 C at the end of the task. It's not so bad if you let the fan run at say 4000 RPM.. not dead quiet like it is under 3500 but still pretty quiet. 2. More annoying, it sometimes idles at 70 - 80 C when I am only downloading a large file and browsing at the same time. The CPU usage is less than 30% and yet it'll be at 80 C sometimes.. dont see a pattern yet but it has been happening. Under normal use though - like right now where a 100 programs are idling and I am typing this in Safari - it idles at 45 - 50 C for me. All in all, I am happy with having chosen the i7 so far. What would make me change my mind is if (2) above keeps happening during normal use and if (1) happens every time I try taxing it. The CPU apparently throttles above 100 C, slowing down the machine.. ---------- Does anyone know of good programs to monitor , control and record fan speed and temperature on a mac? I am using SMCFanControl and iStat widget right now but neither will keep a log of the stats..