Since I'm kind of a Ben fan, I say Widmore was up to it. That being said, I believe Ben wanted to recruit Sayid by handing over the killer. He probably didn't want to meet him right away (he tried to run when Sayid saw him), that's why he had to make up the story of how he got there, but his objective was accomplished nonetheless.
Still, Sayid's gulllibility surprises me. He could have tried to ask Bakir a few questions before capping him.
I believe Ben is not evil, that he would not kill an innocent person (Nadia), but he knows how to take advantage out of a given situation.
P.S. I was right about the boat people being the Russeau and Carl shooters. It was obvious from the start - the others wouldn't have opened fire risking to shoot Alex. Ben is not a cold blooded killer (he had to kill the arab guy and he left the other one alive).