I certainly agree that on a single game basis, +/- by itself can be a very misleading stat, and should be taken with a grain (or 10) of salt. However, I think over the course of a longer period of time, it can be a very useful and telling stat, especially when paired with offensive/defensive numbers. For example, Ime's numbers last year show him to be an effective defensive player, probably moreso than most people here give him credit for. The reasons he gets such a bad rap at times is because he didn't turn into Bruce Bowen (unfair standard) and the fact that he completely fell off the map offensively (fair judgment, and ultimately the reason the Spurs moved on).
Of course, am I saying that Matt Bonner (or Ime Udoka) is more important to this team than TD, RJ, Manu, or Tony? Absolutely not. But I do think the stat sheds light on the idea that Matt is a lot more useful than people give him credit for. Ultimately, though, I can certainly agree to disagree, especially on a stat such as +/- that hasn't been kept long enough in the NBA to create useful historical examples, counter-examples, and analogs.