Here are some bugs i've noticed in KDE

The trash ben doesn't work.

The on screen keyboard doesn't show eny numbers or symbols. especially "/" and "\" and sometimes the keyboard mixes up upper-case and lower-case.

Even thought the login and the logout function is fonctional, you can't login on a N800 without a hardware keyboard.

The sccreensavers don't work.
Some windows are so large, that thay get cut off and you can't see the whole window and it is difficult to resize.

The plugins in koncore are not present.

The hildon desktop is very unresponsive after you exit KDE.

Those are the bugs i have discovered so far. I will post more bug reports when i get the chance.
(Edit) seems someone has beet me to be the first to respond.