So I've been soldering bunch of Xronos boards in preparation for the Maker Fair, and somehow soldered time chip (DS1307) backwards. Obviously it didn't work, although I had no problem uploading sketch. Then I felt a little heat coming from the board when I was passing my hand over it, and then I touched DS1307... and burned my finger... I'm surprised Chip didn't start smoking :) But what a pain it was desoldering it! Don't repeat my mistake, pay close attention how you orient ICs, electrolytic capacitors and diodes (yes I did diode wrong way too once, with less dramatic results, but it took a while to figure out what was wrong).