My experience showed that Irrlicht seems to be rather picky about video drivers, at least concerning Linux.
Heck, on my machine the new Irrlicht version of SuperTuxKart is absolutely unplayable as well whereas my Gallium-powered HD4870 should be more than enough to handle it, despite the driver's experimental status. And you can really see that: The first seconds of a race are absolutely fullspeed, but once it starts drawing any 2D elements on top it becomes a slideshow.