Strengths: You can buy them from ordinary sports shops. I've had three pairs and haven't had any problems. They are really comfortable and offer support for a mild over pronator.
Weaknesses: None that I can think of but I haven't done more than a half marathon.
Overall: I've 'treated' myself recently to a pair of very expensive Asics because I'm training for FLM but the jury's out on whether they're worth it!