From what I can tell it's a cool OS that I'll never get to see because it doesn't run on any commonly available hardware. OP, you can get the "closed box" protection from viruses etc. by using a virtual machine; if you have a modern PC then have a look for the free vmware player (http://www.vmware.com/products/player/
) and then get an image for ubuntu for example or install another OS of your choice on the virtual machine. You can browse the web safely on your virtual machine, and if it ever gets messed up you can delete it and start again.
As an aside I wonder if OS4 has a better chance against viruses as there are a lot of amiga viruses out there, but I suppose they're all 68k only)