My impression is that Glenn Greenwald's reporting is indeed excellent. However my knowledge of secret surveillance is from the writings of people like him - it is not a subject that I have independent knowledge that I can verify anything from. Furthermore at this point I would consider him more of a subject matter expert than a general journalist. Reporting on the same topics in CNN or the NYT tends to be pretty shoddy.
That said, there are some publications, such as Propublica and The Economist that seem to consistently do a good job of reporting. So it is not all. But it is a lot.
That said, I was basing my comments on my personal expertise on programming, math, physics and a handful of celebrities that I happen to know personally. Reporting on all of those is pretty uniformly terrible.