I always meant to post in here but never did but never got around to it. My 3 favorite screensavers for wide/multiple monitor setups are My Pictures slideshow, zMatrix, and UC3D's matrix one.
I don't think that My Pictures Slideshow needs any introduction as it comes with Windows by default.
zMatrixis a little app that pulls double duty as a desktop background app and a screensaver. It can do either of these functions together or independently of each other. Also, it uses very little system resources, and just looks fantastic when you get the settings just right. I don't have triplehead (yet) but I imagine that this would look absolutely amazing on 3 monitors.
UC3D is a screensaver app that manages multiple screensavers from the creator's website. There are only 2 of that I know work with multiple monitors but as far as I know they all work with widescreen. The
matrix UC3D screensaver is very CPU and probably video card intensive however, so watch out. This screensaver may be more customizable than zMatrix, but it's still a toss up on which one would win for me.