Like many other reviewers, I "turned on" to the HP 12C while earning a business degree in the 1980s.  My orginal 12C was misplaced ten years ago, and I replaced it with the HP 17BII.  While the 17B is an extremely functional calculator, I replaced it with a new 12C.  Why?  Mainly battery life (with light to moderate use, I still needed to replace the batteries once a year... with three watch sized batteries, that cost adds up quickly).  In addition the 12C is more compact, and I like the setup of the keys much better.  Processing speed?  Well, I thing the 12C is more than adequate for a handheld calculator.  If you frequently find yourself needing to blaze through complex complications, it's probably best to get out your laptop computer.  Highly recommended.