10.3.9 was my first version of OSX.. actually, it was 10.3, but free Apple updates took me up to 10.3.9.
Aside from the Dashboard and Spotlight, and the Mail application looking a little different, I haven't noticed anything else different in 10.4.8.
There might be some 'behind the scenes' differences, but I sure haven't noticed it.
Two Widgets I use regularly, the Weather Widget, and the Yellow Pages widget. I used the Yahoo versions when I was still running 10.3.9, but I really prefer Dashboard, just because I don't need to have those things on the desktop or hogging up space on my dock.. and I can just hit 'F12' and have them up in an instant, then when i've got the info I need, another tap of the 'F12' key hides them.
As a side note, I find the Weather Widget under dashboard to be far more accurate than the Yahoo version for my area, and the Dashboard version of the Yellow Pages is much faster and accurate.