Well, google scholar certainly does not have all published opinions, far from it. It is not an adequate research tool, just a starting point. I'm not familiar with casemine, will check it out.
EDIT: casemine appears to be neither free, nor to have all published US decisions as far as I can tell.
I also really like casemine.com.
I have no idea how incomplete those archives are but I doubt they’re missing much I’d be looking for.