I enjoyed that I was able to explore an area of business where I did not have much expertise: the field of sales. Being an engineering major, one does not come into contact with the sales profession incredibly often (unless one is a sales engineer by trade). However, I was able to acquire a great depth of knowledge of the profession and will more-than-likely be able to use that knowledge at some time during my engineering career after college. It also taught me how to start and keep conversations going with various customers, no matter who they were. This already has and will end up helping me tremendously in the future during job interviews, career fairs, networking events, and so on.
What I wish was different
I wish that I would have known how cutthroat the sales business sometimes is, so then I would've known right off the bat that I would not want to pursue an extended career in the sales field.
Advice
Don't be afraid to get out of your comfort zone (within reason). A job that you might think to be just a 'filler' job for the summer could be a job that either re-shapes or re-affirms your career choice after college, so choose one at least somewhat-wisely.