I did a master's in CS and one of my classmates in the program was the most competent person I have worked with. She was one of the few people in college or grad school whose work I didn't feel like I had to look over on group projects. This was very helpful, because I had to leave town for a few days before the project was due, so I had to trust her to take my work (which I started a bit earlier than her on) and finish the project without my being able to check over her work. Some things that made her so competent (but that translate into a broader picture of what I think makes someone competent):

- Technical ability: I had utmost confidence in her technical abilities on what was a fairly technical CS assignment. I knew that she understood the source material well.

- Attention to detail: I was confident that she would spot and correct any issues in my work.

- Great communication ability: Technical ability only gets you so far if you aren't great at presenting your ideas. This was especially important for the project at hand since we needed to accompany our technical work with a written report.

- Problem solving ability: She is someone who is great at problem solving and is therefore able to work independently when needed.

- Ability to work on a team: She is also easy to collaborate with and listens to ideas well. If not for great in-team communication, the project would have failed.