I wish everyone could accept the fact that his true value is his third base defense, stop talking about moving him to first, and accept that in general he isn't going to hit for power. He is a great asset hitting line drives, getting on base, and making plays at third. He just might not be the power asset we thought we had. But if we move him to first, I don't really see that he's much use to us at all.
I think Ryan Zimmerman is a next-generation Ken McMullen: great fielder, hits for higher average (than McMullen in the modern dead-ball era), but isn't supposed to be a power hitter. RZim seems like a typical .295 hitter who will hit about 25 homers a season, and plays some of the best defense ever. That's plenty good enough.
It worries me that his slugging % is usually between .450 and .520. Right now it's at .333. I hope it's just a slump.