I loved the idea of three modern women discovering their powers, and the characters were quite interesting at first, but I became increasingly annoyed by the soap-opera nature of the show. It was like the powers were there just to make cool special effects, and seemed to have no real consequences or limitations. It was all about who they were dating, which would be interesting if the characters had any grounding in reality, but they didn't. They were mostly just there to be "sexy".
The women were too powerful too quickly, and were annoyingly stupid about it, especially the redhead. Seriously, you do all these amazing things and haven't figured it out yet? Frankly I don't know how the show could have continued. There was no room for the characters to really grow or develop. When you give your characters godlike unlimited power, how can you challenge them without making them seem stupid?
At least it had a villain, but he was really just there for eye-candy and seemed to have no real purpose beyond winding up Rebecca Romijn's character. I felt cheated by the lack of real meaning behind the magic. A show with three witches will inevitably be compared to Charmed, and it doesn't compare well. The "Charmed Ones" had a definite purpose and well-thought-out rules to their magic.