It's a good discussion list. I think Gionta, when not bicep-torn, is a good player overall who does a lot of little things well enough to make him valuable even when he's not scoring at 35 goal pace. To me, he's fine.
Desharnais is a tough one. He's been talked about so much on these boards (I haven't read it all) that I'm doubtful there's anything original to add. But here goes: I remember when Sergei Zholtok came out of nowhere, on some very bad Habs teams, and played well in a top C role. Those teams were crap up and down, but he looked good. My concern with Desharnais is that he might be that type of player -- a product of opportunity. Sometimes a player with undeniable NHL skills, along with some serious limitations, only manage to succeed on teams starved for NHL depth. Sometimes that kind of player, when properly surrounded and complemented, can also thrive on good teams. I just don't know which he is.
About Moen, I think he's a useful player -- he's an honest checking winger who's strong on the fundamentals of positioning and details. His treatment by Martin and Therrien was very different. As I see it, he was overused by the former, and underused by the latter. Basically, I think he's a solid veteran checking forward, maybe a little expensive, but it's up to Therrien to use him better.
I saw Markov's name a few times, and I would agree, to the extent that the question is: top pairing, all situation defenceman, or smart veteran with an elite specialty who can be exposed if used too much? I think he's the latter at this stage -- you just can't reverse serious injuries and age. But, just to be contrary, defencemen can sometimes do it. To take one example, Aucoin (aka, Augroin) defied all reasonable expectations and kept playing good hockey after he was written off by most for injuries and age.
As for other candidates, I'd say that both Briere and Murray are obvious choices -- but that's natural, given that they were both taken off the scrap heap. They could have a lot to prove, depending on one's expectations. Their success really depends on how the rest of the team does. I predict disappointment if the team as a whole struggles. I just don't think they have it in them to be good players if the core players they're supposed to complement can't put together a good season.