Since you already have a classic machine capable of running the latest OS then you should decide if you want to part with the money required to buy OS4.1 Classic. The OS itself seems to offer a stable environment and it also takes advantage of the classic hardware better in comparison with what OS4 did back in 2007. It's mostly "bug-less" and it offers faster and more stable OWB performance. Don't expect to do many things with it cause as it was mentioned before most of the newer software requires powerful hardware such as SAM/A1. So, i suppose that the main reasons for which to buy OS4.1 classic are:
a) show it off to former amigans
b) only out of curiosity and for testing purposes
c) cause it simply can be done
d)for the geek thing
e) what the heck! Why not?