I just bought a rmbp haswell 8gb/256gb and a mba 4gb/256gb. I noticed that on the rmbp i have 7.5gb used memory with hardly any apps open, just safari. is this a feature of mavericks? y is so much memory used? i know this has been extensively discussed, but apple seems to find only 4gb fit. even the entry model rmbp has only 4gb. so i assume 4gb should be well enough for the mba.does this also have to do with mavericks (which runs on only 2gb theoretically?