Luckily, I went in expecting an Oliver Stone film, meaning that you can't know what to expect, which is what I came out with. I don't feel like I wasted 3 hours of my life, but I don't think I'd spend 3 more of it on seeing 'Alexander' again.
Also, the *wonderful* trailer (which I hadn't seen) for Sydney Pollacks new film 'The Interpreter' was before it ;)