Were the issues with mouse lag on the 2012 model hardware or software related? I tried a 2012 right when it first came out and got physically nauseous from the extreme degree of mouse lag when scrolling. The 2013 never had any problems and I've been using that for the last 4 years.
Definitely a software issue. I have the 2012 model and it would lag in expose. But after the metal upgrade it got a lot smoother. Still gets choppy with many apps, but otherwise smooth animations in most places.
This was completely corrected in software in the next big OS release. It was HORRENDOUS at launch though. It's smooth as butter on the latest version, with the same hardware. Machine runs cooler too
