There is nothing wrong with holding someone accountable, by way of letting them know that you are displeased with the stances that they are taking.
What worries me though is that we(this community) don't always remember that there are differences in individuals, in the way they see the world. The Democratic Party is the party that allows for certain ideological differences because collectively we can band together to protect the value the things we believe in. Things that the other party actively tries to destroy.
While Shuler is far from being a liberal icon, his presence in Congress allows Nancy Pelosi to be in the Speaker role, and for now that's going to have to do. I say, beyond that, we'll take what we can get from him and hope/ask for more.
The guy is already running strong in the NE, and he'll probably win over Michigan's Republicans as well. Throw in Utah, add in his strong showing in Iowa, figure his former moderatism isn't going to hurt him in states like Washington, Minnesota, California and possibly Florida(given Jeb Bush's endorsement).
If I'm on their side, I'd be liking Romney's chances.