My experiments with Hugin's linefind program haven't been very positive so far, so today I tried one panorama both ways, with and without linefind. The results weren't encouraging: without linefind, I had an average error of 0.9 pixels and a maximum of 2.8. With linefind those values increased to 1.6 and 18.8.
And the results? Conveniently it lost the cropping, so these two images (first without, then with linefind) don't quite match:
One thing's clear, though: the first image (without linefind) has better verticals. And that's exactly what linefind is supposed to buy you. Maybe it assumes perfectly level orientation, something that I seldom do. So for the time being, at any rate, I won't use it.