I very rarely use a tilt, only when I want to make a feeling of discomfort or disorientation. In fact, I usually work to make my horizontals or verticals as straight as possible. Almost every photo is cropped/rotated very slightly to make sure it's level.
I think it has to be evaluated photo-by-photo, but unless there is a strong, legitimate reason to tilt it .... just make it straight.
Here's one recent instance where I used the tilt intentionally.
, on Flickr