I've had the Nikon D40 and although IQ was very good, the camera was very inconsistent in terms of exposure. DR was some what limited and I really felt the limitation in terms of lens compatibility due to the fact that the D40 (and since then, the D40x and D60) did not have AF built in. Thus, older lenses (the more reasonably priced ones) would become MF lenses. Add to that the fact that the D40 does not have IS and I ended up selling it after 2 months. Since then I've had the Pentax K100, the Oly E510, the Sony A300 and now I have the Oly E520, which I like very much. Out of the bunch, the A300 definitely has the best LV implementation (the E510/520 sucks in this area, even though they pioneered the system). IQ is also good but the camera suffers from its poor kit lens. I bought a few lenses (Tamron, Minolta) during the period I had the camera but felt that none compared to my Zuiko lenses, reason why I decided to get the E520. In terms of features, both the A300 and the Oly E520 are comperable. The A300 has tilting LCD, which is very handy, specially considering that the LV works so well. This feature would not be as importnat on the E520 because LV is unusable anyway. I still have a Tamron 28-300mm Di for the Sony and looking at the prices of the A300, I might just buy myself one (again). I really like the Tamron lens not only because of its IQ but its versatility. Having that FL range w/o having to swap lenses on a DSLR is priceless (IMO). I recently went on a trip to the California Caverns and took the E520 and two lenses with me. I found it very cumbersome to swap lenses during the guided tour so in the end, I kept the 14-54mm on camera all the time and missed many opportunities to take great close ups of the rock formations. So, with all that said, I'd say the A300 is a great camera for the price. I just wish Sony would sell the body only as many other manufacturers do.