The fancy effects might have something to do with it. It is pretty amazing that the IT is able to achieve these affects at any speed.

I've not used either in a while so, I might be wrong...but the UI in E17 is far more intuitive than the E16 one (more configurable, easier to use).

I'd imagine that some tweaking might make it more usable. Most people seem to agree that E17 runs at least as fast XFCE on X86 processors...so something must be going on. Possibly, the graphical effects are too much for this little guy.