Over the past 30 years of gaming, I've GMed as much as played.
However, in the past decade, I've only run 1 long-lasting campaign (3Ed) plus a short stint as co-GM in a RIFTS campaign.
My players have generally praised my skills as a GM, but that last campaign I ran was decent...but I subconsciously "mailed it in" and was ultimately unsatisfied with my own performance. I had screwed up a certain aspect of the campaign which detracted from its epicness...and didn't catch it until after the final battle. Essentially, I burned out.
I didn't have a good FRP campaign idea for almost a year...but I still didn't want to run a FRP campaign, so I posted many of my ideas in my favorite thread here (see my sig).
Instead, I had a host of ideas for Supers, Sci-Fi, and Modern/Urban fantasy campaigns. Unfortunately, nobody was interested, so we've been going through other peoples' campaigns.
Since then, I've designed a great setting for a FRP campaign and have been writing adventures for it- and now we're playing SFB and Battletech! (Not that I mind, but...)
Someday I'll step behind the screen again, but I don't know exactly when.