Until recently I've not had the chance to try unusual bitters. I've used Angostura and Peycheaud's, also, Collins orange bitters, and gotten good results by my ken.
LeNell and Ben kindly gave me over the weekend a bottle of Fee's Barrel-aged Bitters.
Let me tell you, this is great, and I can see now how a good, distinctive bitters can enhance a cocktail.
I tried it two ways. First, in Old Weller 107 taken down to about 95 proof, with a shot of Angostura added (two shakes of the Fee's, one of Angostura). The whiskey was sweet enough that no sugar was necessary, and it was really good. The Fee's adds a cinnamon/chocolate-like note and marries perfectly with its "cousin", Angostura.
While this was very good on its own, I added half-way through a small teaspoon of (Israeli) Triple Sec. The slight sweetening and faint orange background (the brand I used isn't strong on orange flavor) really "made" this drink. It was an Old-Fashioned, basically, and proved the worth of its storied history.
Contrary to usual practice, I got (in both cases) great results from the unity of one whiskey, but using 40 straights and fine brandy, can be great too, just different.
Thanks again to LeNell and Ben for this generous gift.