I know this question has been addressed, but there's still very little concrete explanation for the difference the memory upgrade makes for the MA specifically. Most folks say just do it, it doesn't cost that much, etc. I'm curious to know if there are a) concrete benchmarks for, say, a new i5 with 4g v. 8g RAM; b) personal anecdotes from people who have used an MA with both memory configurations; or c) an explanation from someone with technical knowledge who actually has a sense of the working conditions in which the memory upgrade might make a difference (I use the web and MS Office, and I often have several Firefox windows open at once for research). For the sake of argument, let's just say the $100 is a big deal and that a compelling reason would be necessary to make the upgrade. Also, I'd rather go to my local Apple store tomorrow rather than wait a week on BTO. Thanks!