I was planning to buy the Compendium. All the rules, with all the up-to-date errata in one package sounded great. The Essentials classes left me pretty cold, but I figured I could ignore them. However, there is a major errata deluge scheduled for October that may just about re-write the game. I'll have to wait and see what it's like before I pick up the Compendium.
Fortunately, D&D Encounters seems like the perfect venue to try out Essentials. It's free, we get to play a classic module, and see what it's like. If it sucks, oh well, editions are like busses, if you can't get on board one, just wait a while and catch the next.