He was great on TNG, but I think he was used far more effectively on DS9. One thing that always impressed me about First Contact is that it's the DS9 Worf who returns to the Enterprise. It would have been easy to have him just slot back into his old relationships with that crew, but instead we have a Worf who has learned from Sisko, and challenges Picard in a way I don't think he would have on TNG. It's the perfect example of his development as a character on DS9, and it's a shame that in INS and (particularly) NEM we seemed to get TNG Worf again.
*jaw drops* You are my hero.
It would've been nice to have a scene where, after Worf and Picard blow up at each other, we see Picard grumpily heading back to the conference room, audibly muttering under his breath, "Goddamn that Sisko, first he rags on me about his wife, now he turns Mr. Woof against me..."