Finally handled the E-510 as well, and I have to say that the IS is indeed impressive. Hope the durability of IS would be proven over time. This has been my biggest concern.
After handling both new cameras from Olympus, I have come to my little conclusions and opinions about the two new siblings to the Oly line of cameras.
About the E-410 :
Contrary to what is being marketed, I feel that the 410 is really the "Digital OM" of this era. Well built little bugger, and really feels solid in the hands. A very well built camera indeed. My biggest complaint is of course, as a E-1 user, the built in WB sensor, which cannot be compared to the E-1 at all. Shot after shot, the E-1 still produces very good images. But this is something that can be fixed in post.
Regardless of what the marketing people or reviewers has to say about 410, I would not recommend this camera to girls or novice in digital photography because it does not have the newbie friendly IS. (After handling the 510). You have to have basic knowledge in photography and am able to hold the camera well to shoot good pictures with this camera. Your left hand is more important now, as the right hand is kinda useless as the 410 does not provide the grip like the 510. Therefore this is a camera for the old school photographer. Someone who has been shooting with the right techniques and have developed a good and proper handling of SLR cameras. Left hand balancing the lens and camera body, the right hand left free to shoot. If you get your hold right, then this is the camera for you! It is a joy to shoot with this camera, except for the WB issue mentioned above.
About the E-510 :
I have to say that this is the most newbie friendly camera with professional functions. But like the 410, it also does not have an external WB sensor found on the E-1. But the handling of the camera is very forgiving. You have good grip on the body, thus making it easy for a novice who does not have the basics right for handling cameras. The kit lens is equally pleasing though I am already spoilt by the higher end lenses.
Everything that the competition offers in an entry level camera, the 510 also almost have it all, and surpasses many cameras in its price range. This makes me wonder how impressive the new Pro and Semipro camera bodies will pack. Really anticipating their release.
The IS really helps the novice when they are trying to learn their basics, but I keep wondering how robust is the IS engine. This will tell over time. But again, for a novice, I will highly recommend this camera. This is the modern Olympus DSLR as compared to the E-410 little brother.