I've recently developed a site using Xoops2 and was very impressed with the xoops engine. I've fully integrated OSCommerce (a scaled-down version). I needed to heavily customize and hack OSCom to behave itself w.r.t Xoops2 session management.
I addition to this I believe I've struck on a limitation of sorts when it comes to customizing boxes for Xoops. Normally CSS would work fine for laying out the boxes. My boxes had graphical borders though, which means I ended up hacking my graphical borders into the system templates (ouch! .
Have a look at my site and I'd appreciate feedback. http://www.cafelinux.com.sg
Cheers Stephan PS: If anyone knows of a neat way to layout boxes with graphical borders using CSS, i'd *love* to know about it.