I am trying to print Emmett’s Secret Heart Box http://www.thingiverse.com/thing:44579 in PLA and the top is not bridging properly. The rest of the print looks great! It was printed at the lulzbot supplied medium pla settings but with a 20% infill, 3 perimeters, 4 top, 3 bottom. Speeds, cooling, etc were not touched from that ini.
Here is a picture and you can how none of the top parts made it all the way to the side. the bottom section of the top did better with its shorter distances but the first layer of the top also did not full bridge there also but but the time the 4 layers were done it was at least closed.