Scotland in May is hard to beat. The weather is starting to clear up, the midges haven't woken up yet, and you can actually get a table at a pub in Edinburgh without waiting an hour. Driving up through the Highlands when the heather starts to green up is worth the flight alone.
A typical trip runs around $3100 all-in for flights, lodging, and getting around. Spreading that cost out over time makes it manageable instead of a massive hit to your checking account all at once.
That 0% window is a deadline, not free money. If you still have a balance left on the card when the 15 months are up, interest kicks in on whatever is left over.