Generally ... if its not broke ... don't fix it. That said, 4.1.2 is a perfectly acceptible version to be using. 4.1.3 (4.1 SP3) is out; and SP4 is due out shortly (hopefully this week).
Bookmark this: BlackBerry Technical Solution Center
and check the link for Product Documentation
There isn't anything groundbreaking such as the ability to host a BES on a toaster or anything in 4.1.3, but check out the documentation and see if any of the fixes / features apply to your org.