Steve Litchfield of AllAboutSymbian has done a review of the latest version of Smartmovie which claims to play movies at 24fps with the new CoreMP4 open source codec.
Currently even I like Smartmovie and am sticking to it. But once the open source free TCPMP project is out of beta, I will switch over to it as it offers support for many other formats without the need for conversion!

Read the full review here