Whether the ACA is a economically sound policy, I do not know. After all, it's modeled after the Republican alternative to "Public Option" system preferred by the liberals, and it's quite analogous to social security privatization which up to this point the Republicans have advocated. (They might have changed their mind on that by now, though.)
But is it Constitutional? Resoundingly yes. I understand people have gut feelings and senses of righteousness, but those are not exactly a legal argument. The constitutionality of the ACA is quite straight-forward if you have followed our system of the past century.
The current misunderstanding is best understood as self-fulfilling prophesy. You keep repeating something and people start to doubt.
Roberts has a lot of hot cases waiting in the wings - Voting rights Act, states' vote-supressing laws, affirmative action, states' policing of immigration, same-sex marriage, unresolved questions on gun rights and campaign finance, etc. Oh and the increasingly obnoxious states' anti-abortion laws that are enacted for the purpose of reaching the court (with the obvious goal of Roe v. Wade reversal) may eventually get to the court as well.
The ACA hearing is kind of like a political theater for the court to redeem itself, after the backlash of Citizens United. Roberts deeply cares about his reputation and his courts'. There is no doubt in my mind he will write the majority opinion affirming the constitutionality of the ACA. Once all the craze around the ACA quiets down, he will silently go onto dismantle aforementioned precedents.