Travel helps you sort out feelings quickly
Travel forms a bond between two people or drives them apart -- solidifying any on-the-fence feelings you might have. They will either become your very best friend or your sworn enemy in the course of a long weekend.
In fact, if you're wondering if you want a future with your boyfriend or girlfriend, travel with them immediately. Sometimes it takes being in a new place to really put things in perspective. (Although I would suggest keeping that first (last?) trip within driving distance so you have an escape if necessary.)
True colors can't hide on vacation
Unless you book separate rooms, traveling with your S.O. basically means spending 24 hours a day together. That, paired with the unpredictable factors of any trip, means there's no place to hide. You're about to learn quickly whether your boo can read a situation, problem-solve, and handle his or her shit in any circumstance.
If they can, this person is a keeper.
Communication will be tried and tested
Communication is essential to the health of any relationship. And nowhere will these skills be tested quite like while traveling together. If you can talk through disagreements while far away from what you know and your daily routine, you are on solid footing as a couple.