The only issue i have with the Olympus is finding used Olympus lenses. I have a couple nikon lenses that i use with adapters, but only the stock 14-42mm 4/3 mount lens.
If i had more cash to go get new lenses this camera would be 10x what i use it as. But for the meantime, buying used lenses and adapting them does the trick
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also... no HD video on the E520... there's been times when that would be nice.