I don't know if Joymax did any detailed shadows fixing, but Ubuntu (or any Linux I'd assume) definitely makes detailed shadows work a lot better. With my old desktop:
AMD Athlon XP 3200+
512 MB DDR PC2700 RAM
nVIDIA FX 5200 AGP 128 MB graphics card
in Windows XP, I had to run the game on "Low" graphics (but could set draw distances to 3 or 4) in order to get the game to be playable. When I installed Ubuntu to play SRO, I was able to set graphics to "High" with every feature turned on including detailed shadows. The only thing I turned off was water reflection.
On that system, with Ubuntu, and high graphics settings, I didn't have much lag out on a grind. It did lag like crazy in Hotan and other towns when crowded, but that was more because of the 512 MB RAM than anything else. Detailed shadows still worked.
I have SRO installed on an Ubuntu-bootable USB thumb drive (info in my sig) that I can run on any system I want. I played it a bit on a core 2 duo with an integrated nvidia and 2 GB ram, and I get almost no lag in hotan on high graphics and detailed shadows.
I can't wait to try it on my new system when I get it built (it's sitting in boxes right now). AMD Phenom X4 9500 quad-core (64-bit), 2GB DDR2-800 corsair, nVIDIA GeForce 8200 integrated. I suppose it could be better, with extra RAM, but it's a quad core

and Ubuntu certainly doesn't need as much RAM as XP does. 2GB shouldn't be too bad.