Here's what I think Darcy has done well, and it can be boiled down to a few simple trades. simply because he's lousy in managing the roster he has.
He overpays for favorites, hangs on to them for way too long until they either walk for nothing, or their value has hit rock bottom.
Barnaby for Barnes = Good deal, Barnes could still play the game, and clearly Barnaby didn't want to be here anymore.
Wilson and a pick for Warrener = Absolute steal, Wilson was a bust if ever ther was one, and Warrener was in his prime.
Gratton for Briere = Good deal, but overshadowed by the fact that Gratton was brought in for three players, including Corey Sarich. Still a steal though, as Gratton was a huge bust.
Warrener and Reinprecht for Drury and Begin = Well, let's just call it Warrener for Drury. Good deal, was sad to see Warrener go, but Drury turned out to be something this team sorely needed after Peca left.
Drafted guys like Pominville, Vanek, Myers etc., but overpaying for each and everyone takes away from the positives.
That's about all I feel he's done well over the years, and for everyone of those deals, there's a bad deal and an overpaid stiff.