I've never worked full time anywhere before, but the pay was amazing, like double what I expected. And I was getting paid to program, which is something I love anyway. I learned a ton, had as much fun as is possible at work, and got paid enough over one summer to cover most of my college expenses for a semester. The people there were super friendly and helpful and I could definitely see working there someday.
Working full time is not fun, no matter what you're working on. But honestly, that has little to do with the internship itself. I don't think I have any thing I liked "least" other than having to be in the office for 8 hours a day.
Advice to Potential Interns
If you qualify for this internship, you have nothing to lose. I have had no regrets taking this opportunity.