I returned a 2009-model 2.8GHz i7 27" iMac due to high pitched electronic squeal coming from the LED Inverter board. It was quite loud and very annoying. I got a full refund for the unit and purchased a Mac Pro instead. I'm thinking about purchasing a 2010 iMac for work. Is this an issue on any of the 2010 models, does anybody know, or has this issue been eliminated completely? Thanks!