We were very pressed for time in Edinburgh and only managed a 30 minute visit to St. Giles. That was a mistake, as there is enough to see in this beautiful cathedral to take up at least an hour or more.
We gladly paid the 2L photo fee and happily snapped away at the stunning gothic architecture. In our opinion, this was just as worthwhile as Westminster Abbey, but well more beautiful.
Should be on your top 5 to-do list in Edinburgh.