JMO...
funny thing i've used all 3 of these cameras! one from school, one is my sisters, and one is my friends.
nikon d50..to me it seems like it doesnt compete with the rebel, the d70s is the rebels competition. anyways, if you know how to use the camera and use all the custom functions you'll be great with it. oh and since its so sturdy it feels great in your hand. + it has the rubber covering! very ergonomic, i love the placings of the buttons and the dual select knobs..front and back.
the olympus i havent touched as much cause its my sisters but it has some nifty features.. the sensor cleaning feature is really cool and its a first in the dslr market.. and the lenses are digital lenses..i dont really know how to explain...it...anyways...it has very cool features that normally come with point and shoots and if you need help making the transition from P&S to DSLR go for this one..my gripe? it has a cheap plastic feel to it and feels like you could scratch it up so easily.the rough kinda plastic, know what i mean?
rebel...what can i say, better iso quality than the D50 thats for sure, against the olympus im not so sure.great iso quality...bang on awb... gripe? its small and once again has that cheap plastic build quality to it.....but produces great results. get the battery grip if you think about getting this.
in the end, try to see if you can get all 3 together on a table and just hold them, play with them, put them up to your eye, try out the different lenses and see whihc one you feel most comfortable with beacuse talking and talking means nothing without feeling and seeing and trying. :-)
i feel like i should clean this up but oh well at least i seperated it into paragraphs. 