It should be noted that making things static can impair testability a great deal. For this reason I frown upon static references across component boundaries. Even within components I tend to use dependency injection for this very reason.
I fail to see why static methods should be better with respect to maintenance unfortunately the author lacks an explanation of this opinion. I would express the contrary opinion as you can exchange the implementation easier at selected spots.
It depends a lot on what you do with the static method. If it's side-effect free, an Utils class with static methods can be a good way to test some business code without exposing private methods.
Yes, the Utils class is easier to test. But its clients are harder to test, if the Utils class crosses component Boundaries or rely on a fat runtime (such as an JEE server or an OSGi runtime) being up and running.
For some cases. But static methods can be easier to unit test.
But if you're concerned enough about performance to care about minute bytecode details (intended audience of the article), I think ease of testing is a lower priority.
I fail to see why static methods should be better with respect to maintenance unfortunately the author lacks an explanation of this opinion. I would express the contrary opinion as you can exchange the implementation easier at selected spots.