Thanks very much for the bitters descriptions. I'll have to give the Regan and Woodford varieties a try in some upcoming Manhattans. And I agree, the barrel aged Fee Brothers can be tough going, but if you have a chance to try their orange variety, I don't think you'll be disappointed. And they also combine nicely with a dash of something stronger, like Angostura.
The local stores finally got some DSP-1 Rittenhouse in stock, so maybe I'll have a Manhattan-off with the baby Saz and the new Rittenhouse and see what's what.