After using it for nearly 2 months, I have found it useful for getting links to other resources. I follow key people and have gotten some great tips for good links and resources. After a month or so of use, I found that I didn't like following people that post too much. It becomes too much to filter through for the casual user. So I edited who I was following as a result. I also protected my profile. Although being a fan of open use and transparency, I had a few sketchy people start following me. I will say that Twitter quickly disabled some of these questionable accounts before I could even view who they were.
I'm still not an avid Twitter user but I check it a few times a week and post blog updates and an occasional thought to share there. Overall, the jury is still out for me but I do see some definite benefits of Twitter for professional growth and links. I also see how it can be a grand waste of time if you don't filter your lists and keep its uses intentional and focused.
It is similar to many of the tools that our students use. It's not about the tool, but how it can be leveraged to benefit our learning.