Mod idea...
im not sure if this in the right place or whatever... but here goes...
i have no idea about modding portal or even if its fully possible (the best iv done is made a big open cube in the map editor), but i was wondering wheter it would be possible to make a mod which counts time (like in the challeng maps) in milliseconds, rather than just seconds..
i was trying to see how fast i could do chamber 13 today, and realised it would be so much better if i could see more acurately my time... rather than it just be rounded off in seconds...
if anyone has any ideas of how to do this or know if it could be done post here... 
No clue, but I think this type of topic may belong in Maps and Mapping...
*fifty cakes fall out*
Time out for a second. That wasn't supposed to happen.
i'm sure it measures in milliseconds, (or rather hundredths of seconds) but as to how to display them, i'm unsure. might check into it later.