This is true.
I found a decent 28mm vintage Vivitar 2.0, but I think it appears softer than the Tamron at lower aperture. The Tamron is great for wide angles, fair enough, and that's why I'm glad I have it, however I agree that it would not be OMFG worthy.
I'd say the Helios 44M fits the bill of an OMG lens. The Tamron 17-50 2.8 is a workhorse and great for documentary shooting or when you need something wide. If you're on a crop sensor camera, that should be one of the first lenses to get.