http://www.youtube.com/watch?v=55Q_Uk0ql7Q
shows the difference between software 3d and the gpu units in the N900.
needs to be back in the range. the N95 had one that wasn't used
but the market has changed, now its a necessity in the new app focused world.
The N95 (and the N95 8GB, and N82, and E90) had GPUs that could be used by any app using the OpenGL ES APIs.
Since those models, there has not been any S60/Symbian based phones by Nokia with a GPU (3D hardware acceleration). As you note, the N900 based on maemo (Linux) has one.
Nokia has not announced any new S60/Symbian devices with a GPU. That doesn't mean that there aren't any forthcoming, but we'll see it when we see it.