Great Choice... welcome to the fascinating World of photography! The Sony A300 is a brilliant choice with loads of features at an awesome price tag!
My choice would have been the 450D (Or the 1000D more preferably considering your budget would have fetched a lot) since the Canons have an edge with Noise... they are the best at maintaining Signal to Noise ratio. They also have a wide variety of lenses catering equally to the consumer and pro segments with something for everybody in the bag!
But I do believe its worth mentioning that though Im nowhere near being a fan boy but owning a Canon system does make me biased!
What I like about A300:
>Flawless brilliant Live View (for a DSLR) with a.. whoa.. articulating LCD!
>9 Point AF (though its not going to have much effect in the type of photography you'll be doing unless you shoot lots of birds or bikes.. moving of course)
>Built in IS (once again its a good feature to have but it probably wouldnt have bothered you "NOW" untill you get a tele lens)
Once again... congrats and happy shooting! Do post your Flickr account or at least PM me!