I am in the market for a dslr and these two cameras are very similar except for the price. I can get the E510 with the two lense kit for less then the one less kit with the pentax. I like the pentax because I hear about its very good build quality and dust/moisture resistance. I also have seen cheap telephoto sigma lenses for the pentax and it seems that theres alot more lenses (specifically cheap ones) for the pentax. I will mainly be using this camera for outdoor pictures so having better build quality and moisture resistant would be nice. However, I am a very careful person so I could probably get by without those features. However I feel you get more for your money with the olympus and with the two lens I will not need to get another lens right away as I would with the pentax.