Flexible schedule, good pay, projects were on topics that I found personally interesting.
What I wish was different
More variety of work could have made it better, and perhaps more involvement in the drafting process. However, these things definitely depend on who your PI is.
It's very important to build connections with people, at school, at home, at work, etc. If you get to know professors, etc. at school or near home, they can often provide you opportunities that you would be hard pressed to get yourself.