It feels slower than my C750, probably about the same as my sl5500 (we're talking about running X11 here).
In fact the menu behaviour etc (slight delays) reminds me of my Psions (Series 5 probably) - it's slower, but usually not so slow as to be annoying.
Si
P.S. If someone wants to compile this:
http://gtkperf.sourceforge.net/, I'll run some tests (as it's available for the 770).
If you want me to test other stuff (like fp speed which will be slow as it uses FPA to remain compatible with debian), then let me know, and give me some ideas of what to use to test things, etc.