I filed a bug report some time ago here: https://sourceforge.net/tracker/?func=detail&aid=3002665&group_id=55736&atid=478070
Just tested this with Pd version 0.42.5-extended-rc2 on Ubuntu 10.04 and it's the same. Basically I get two events for each key press like this:

[hid] opened device 4 (/dev/input/event4): AT Translated Set 2 keyboard
print: key key_space 1
print: key key_space 1
print: key key_space 0
print: key key_space 0

Thought I'd mention here too as surely this is a bug? Not a major problem, but it means I always need an [alternate] object or similar. This then became a problem when working on a patch for two note chords when the key commands do not always arrive in the same order and some notes would stay on.

James