I like the 7D because of its functions and interface on the body. Their G lenses are very good as well, just a matter of time when they put 'Ultra sonic'-like motors into them, they will be perfect. Minolta's always been known to make great bodies. Pics straight out of the camera looks VERY GOOD.
The D70 I think is the best value DSLR on the market now. The body is good ( big buffer, fast, easy to use, LCD looks good, matrix metering-it sees the world in colour unlike other makes, very good flash system, 1/500 flash sync, etc. ) And lenses needless to say, very good, huge selection, even for third party ones the support very strong. Note: No batt/vertical grip as of now.
The 300D is cheap, more 'limited' in regards to functions on body. Noticeably slower than D70, both in writing speed and startup time-3 sec, the D70 almost immediate-0.2 sec? Rather go for a 10D if budget restricts. This is what I am using by the way.
Oly I don't really like. But I do like the E-1 body, the way it feels. You have to hold a E300 to see if you like it. I did, can't say I love it. Please go and think about what kind of lenses you are planning to get. Althought I agree that the 4/3 system is a GREAT IDEA, which make everything lighter BUT they actually charge around the price of the rival's 600mm lens for their 300mm f2.8 because effectively you do get 600mm on it. ( 2X multiply focal length ) My name is NOT ROBERT.
Going for N or C has another plus, as many owns them as well. Buying second hand, selling stuff or even borrowing stuff from friends is much easier.
Just my thoughts