Two weeks ago I bought a new Panasonic plasma 42" TV, with inbuilt Freeview HD and Freestat HD tuners.
The picture quality is really outstanding on ordinary freeview. To be honest there is not an enormous difference when viewing the same transmission on Freeview HD. Yes, it is perceptible, but you have to look quite closely to notice it. I have not tried Freestat, so cannot comment about that, but I guess its similar to Freeview HD.