As has been mentioned, the camera is small and lightweight, but nonetheless it is comfortable and easy to hold. I sometimes feel that smaller cameras with a protruding grip are difficult to hold - the Canon EOS 350D springs to mind, as the purchase tends to be too small for my long slender fingers. This isn't the case with the E-420. It's traditional flat styling allows the camera to sit neatly cradled between my fingers and the palm of my hand. A minor criticism is the protruding strap lugs which can dig into your finger a little - if they were more flush, it would be more comfortable and streamlined.
The viewfinder is a mite difficult to see completely. Even though the viewfinder area is small, something that is typical of the Four-Thirds system, it's difficult to read the viewfinder shooting information on the right of the main screen. Shooting in bright conditions hampers this more - the green LEDs are too dim to see and I had to resort to using the main control panel on the camera back quite often. As this entails repeatedly taking taking my eye from the camera it soon became annoying.
The Live View system and LCD are bright and usable even in very strong sunlight, though I still prefer an optical viewfinder for composition. While I appreciate many of the benefits of Live View, I prefer the tilting screen versions. Shooting low or high is to me the major benefit and fixed screens by their nature don't allow that.
There's some debate about the value of the main control screen accessed by the LCD. Some people prefer more direct access buttons, some people don't. Personally I like the Olympus and Sony system of quick access via the thumb pad and scroll wheels. It generally works quickly, and once you get used to it it's very intuitive. It's also good to quickly check all your shooting parameters in one go rather than go through menus or a million buttons. I've lost count of the time of the times I've grabbed a camera to shoot, only to find that I've left it in some weird set up from the last use and ruined the picture (the benefit of raw shooting is that often this is fixable).