Cuomo seems like he could be strong, but his economic positions are way too conservative while the only things he seems to really be leftist about are gay marriage and abortion. I don't think I could vote for him.
Schweitzer seems a bit more promising, and I haven't really heard too much about O'Malley. Not a huge Gillibrand fan.
Cuomo's position on gay marriage puts him to the left of Obama on one issue, and he's obviously hoping that strong leadership that one issue will offset being lame on everything else. Taking down Cuomo in the primary would require some work, New York governors usually get the nomination when they want it.