I have a confession to make. I was one of the people who thought testing is a crappy job that anyone can do.
I realized the value of a good tester when I had the opportunity to work with one. My AHA moment was when I read a bug report posted by a tester in my team and the first reaction was "How the hack did you thought about that scenario?".
As a developer, I always consider the code that I write my baby. When I'm thinking about test scenarios the two sources of inspiration are the specifications and the technical implementation. Is this enough? I thought it was, until I've met testers that proved me wrong.
After having the opportunity to work with testers that gained my respect, I changed jobs and I realized what Dr. Seuss wanted to say with "Sometimes you will never know the value of something, until it becomes a memory”. I was missing passionate, thoughtful testers that understand software both technical and business aspects, who look at the software that we write from a different perspective.
I am not a tester, so I don't evaluate a tester by the criteria you can find in a job description. My criteria are empirical and come from 10 years of working in IT and participating in both development and testing conferences.
The most important criterion is the value that a tester brings to the software that I write.