If you've never used one you wouldn't know
Many people became Olympus owners after drawing up a list of several manufacturers and trying them out in the shop. Several Olympus users I've known went the Olympus route after doing this, whereas many Canikon users I know never tried their cameras before purchase - only read reviews or listened to sales people.
My personal choice was the Canon 450D, Nikon D3000, and Olympus E520. After fiddling with them and trying them out for some time it was clear how much nicer the Olympus was to use.
Obviously, it's just perhaps my preference....
And this is Olympus' and Pentax's problem. Most consumers never get the chance to try them out, and the E5 will be no exception.
Panasonic G3: 9-18mm, 14mm, 20mm, 45mm