I have a Sony a200 and I went through similar decisions as your going through. I was choosing between either the Canon 450d, Nikon d40 or Sony a200.
While I understand that the Canon is arguably the better camera of the 3 I went for the Sony over those 2. Canon and Nikon both have great systems like others have said, but I really like where Sony is heading and they are adding new lenses and cameras all the time. I wanted a base entry camera and the 450d was a lot more expensive than the Sony and Nikon and you may think that is short sighted to pick the cheapest, well yes maybe, but not all of us want to make money with photography, we do it because we enjoy it and some people have generous budgets and others not so.
In summary I was able to get the a200 with the kit 18-70mm lens and a 70-300mm lens for less than I would have paid for the Canon (at the time, I don't know what the prices are like now).
I also thought it was a better camera than the aging d40 which my friend has, nice camera but has been replaced, Sony was an excellent price for what I think is a great camera. As I have not spent a fortune on Sony equipment I am not yet locked into the Sony system, but with the purchase of another lens I probably would become part of the system, and tbh looking at the higher end cameras and what people have been able to capture with them I can honestly say I am excited to be part of it.
Get to a camera shop, hold them, test them, research, decide what you want to shoot etc and go for it. The Canon and Nikon are more stylish than the larger, heavier black Sony, but I couldn't be happier with it - and if you want live view the a300 is not much more and is the same camera with live view.
Like the poster before said everyone will defend their own brand, I am not saying mine is the best because it isn't, but its perfect for what I want, and sometimes on forums people fail to realise that some people dont have money to waste or see it as a job opportunity, get what makes you feel happy, my friend would come on here and 'big up' his Nikon and my room mate got the 450d for Christmas and he would big up his Canon - of the 3 the Sony feels the 'cheapest' - but I love it and there is not one shot that my 450d mate has taken that looks better than what I have got - its just as much about the photographer as it is the camera!
Look for reviews and make a shortlist then get to a shop and see what you like.