I would say sell it. Never had a Hassy, never really wanted one, but I have been in a similar boat: in one case, I was lucky getting a slightly rare, very sought after lens for far too cheap, and was excited to see what the hype was all about. It was a steal, and now I had some gear I could never afford usually/never justify. The thing is, it never did anything for me- I didn't see anything special with the pictures, it was in a range already covered by my other equipment, and this particular lens was kind of heavy. Plus, knowing it was rare, I didn't always want to bring it out- I couldn't replace it if I dropped it- I used it a few times then it just sat in one of my gear cases.
Eventually, I sold it, picked up something I needed (a new 35mm body), and have now taken thousands of pictures with that- whenever I regret selling it, or when I see one for sale with some astronomical price, I remember those thousands of pictures. How many pictures did I take with my exceptional lens- maybe one or two I remember, but nothing spectacular. It's gone, it was the right choice.