What's interesting is that the Virginia judge, the Hon. Henry Hudson declined to apply severability principles. To justify that decision, that judge had cited a 2010 Supreme Court case where part of the law was invalidated but the rest retained (Free Enterprise Fund vs. PCAOB). The big difference? In that case, the law was passed by a nearly unanimous Congress -- and it would have passed even without the provision being challenged.
Here, obviously, that's not the case. The individual mandate was at the heart of ObamaCare -- the law doesn't work without it.
Onward to the Supremes.
Update: It's also worth noting that Judge Vinson didn't buy the states' arguments about Medicare -- in short, he found under existing precedent that it's permissible for the federal government to condition continued receipt of Medicaid funds on their acceptance of the rest of the ObamaCare regime.
Thus, it's clear -- as many already expected -- that the individual mandate/Commerce Clause issue is the strongest legal argument ObamaCare opponents have.