I must admit that, although I didn't like the fact or the events surrounding it, I found the Hopeless Charge (Faramir to Osgiliath) to be a very sentimental scene. Especially with Pippin's little "All Shall Fade" number.
But beyond that, it didn't make sense. Why send a whole bunch of troops back to retake a beaten down mass of stone? I think it's smarter not to spread yourself out in the situation Denethor was in. But then, he was a complete idiot and a jerk in the movies, so that fit well with his character.
In short, it's like everything else. It looked good, but made no sense and was completely non-Tolkien.