I'm very interested in this topic and look forward to other responses. 

I've found the book, he End of Performance Appraisal by Armin Trost to be thought-provoking.  It's a bit academic but addresses the limits of traditional approaches, what kind of company culture or job structure is conducive to ditching the annual review and finally, a description of alternatives to performance appraisal.

Good afternoon!

I would not call them IDP's - those bring up negative connotations of poor performance (remember students in school?).  For nearly 20 years, we've encouraged our clients to get rid of those old school annual performance evaluations as they are pretty useless, and the courts don't like them.  We call our system "Growth & Goals."  Some of our clients do them monthly and some on other schedules, but not more than quarterly - your business changes so fast, and employees' skills need to adapt quickly.   These Growth & Goals meetings give specific learning and performance targets based on their job description and growth desires/needs.  If a manager doesn't have time (or desire!) to sit with their direct reports for an hour each month to discuss this, either they are managing too many people or they shouldn't be managers.  Plus, these more-regular meetings are a good way to head off problems, and maintain good relations and retain your talent.