i use verticals, almost all the time
horizons are almost always not straight, as they might curve in and out, but verticals, from buildings if possible are unlikely to do so (except maybe the leaning tower of pisa)
of course, when using verticals (and horizontal lines too) be careful of distortion, other than barrel distortion like the keystone effect and some others, cant remember the names
so when using verticals, try to check with those as close to the centre as possible