I have really come to like this package, and, no, the built-in units handling in newer versions of Mma isn't a match for it by a long, long stretch. With some minor editing following the author's suggestion in his December 3, 2012 post, it worked fine in Mma 9 and 10. Unfortunately, there's more severe issues in Mma11. Trying to run the WorkingWithUnits notebook available here, there's a bunch of error messages and empty plots that appear. Is there anyone out there interested, knowledgeable, and kind enough to take a shot at fixing the package? My feeling is that the author, working for Wolfram, doesn't want to interfere with the direction that Mathematica is going in that area. Me, on the other hand, I still think his package gives much more convenient units handling than native Mma.
Sorry, I guess your message got spam-filtered. I had a quick look at the package under Mathematica 11.0.1 and fixed the problem with graphics commands not applying the new Units rules. I didn't see any other problems. New version is available here: https://download.wolfram.com/?key=XD81Z7