4e has really liberated me as a DM. I can focus on fun and creative stories, less on frustrating minutia. I really feel I have a handle on the crunch, and the chassis really allows me to build the worlds I want without the sacred cows and built-in assumptions weighing on me. The official and third party technology has been outstanding, as well. Clean, balanced, malleable, easy to design for, and with so much room to grow yet.
I'm running the best (and longest) campaign of my life using these rules, and having talked with my players we agree we've found our perfect iteration of D&D.