I have to be honest and say that they're not something that I would personally use in my projects for a number of reasons. First of all they are quite flat and plain looking. As a web 2.0 designer I prefer something that stands out and when I look at these I can't help thinking that they would be better with a bevel effect and a slight drop shadow on the text and maybe some lighting effect to make them glossier. I think that from a developer point of view, they are much too wide for effective use in web projects. Because so many people are on multiple social networking sites I like to have social icons floated side by side so I can line up quite a few in a shorter space.
Don't be discouraged though, it's always good to see new social icon sets & I think you just need to maybe take a look at what's being designed at the moment as these ones unfortunately look a bit dated.