I have to say, I was in a similar situation to you, trying to decide how much I liked photography vs how willing I was to have a big clunky camera.
I was weighing up the G9 and the S3 IS or something similar. At that point I was into taking lots of pictures on holiday, and starting to explore different settings in the menu, but nothing more than that.
I ended up getting the mighty Nikon D40 even though I wasn't sure if I really wanted an SLR and I am so glad I did. Plus point of an SLR:
- exceptional picture quality (having a better camera won't make you a better photographer, but you will see your images improve)
- zero shutter lag - a big plus point for me
- that proper camera noise when you press the shutter
- the ability to change all the settings
I have to say that if you are thinking about getting an SLR, then you probably should get one, and you are unlikely to regret it - don't worry about the bulk, they aren't really that big especially the XTI or the D40.
That's exactly what you get from an entry level camera such as any of the XT series, except that the XTi includes Live View (?).