The 64 bit 27in  iMac is a disaster! I have used apple computers for 20+ yrs. If your a mind reader you wouldstill be lost.  some pointsMany features... But they are buried under many layers of other soft ware. Many new features are gimmicky.You will need to purchase new software  to run many programs from your previous 32 bit iMac.What took you one step now may take you 2 or 3 on some programs.The menu bar for email (yes simple function like email menu is twice as long).Apple Care  some first line advisors will be unable to answer your questions. Best get to know your favorite senior adviser.etc....