Without knowing the application, and exactly what's defines "super slow" it's hard to anyone (including VMware) to say why you're seeing a difference in performance.
Fusion doesn't implement OpenGL for 3D acceleration - only DirectX 11 at this time. If your application can use OpenGL, it may be falling back to using software implementations when running on Fusion - which could explain slowness.
If by the "other platform" you mean Parallels, they do support OpenGL.
- Paul (Technogeezer)
Editor of the Unofficial Fusion Companion Guides
