Been thinking about trading my 13' macbook pro for a imac. Powermax quoted me $700 trade in value. Does iMacs usually last longer than MacBook pros? Im still kinda iffy about it because I heard horrible things about all in one desktops. Also have anyone ordered thru this company? I see they have a 27' iMac for about $100 more than a new 21 inch one. Is it worth buying used? Any suggestions?