Yes, hazelnuts are tricky. There was one that Neepsend did a couple of years ago - I came across it when I was scoping the pubs in NuL for our pub crawl there. It was very subtle, with the nutty flavour developing gradually. If the proportion of nuts had been wrong it would have been nutty to start with, then nuttier and nuttier. Subtlety is the name of the game (and not just with hazelnuts, I would say).
Sounds fascinating. Was it sweet? Or bitter? I once made a wine with rosehips, but it was a lot of hard work for a not terribly rewarding result.