The science: One of my collaborators supplies interesting molecules to lots of people. Six months ago, my student and I wrote up a paper on our measurements of some of these. We were pretty pleased with ourselves, because our data lets us make a pretty strong statement about the underlying conduction process in this system.
The sociology: While we wrote this up, a competing big group had been doing measurements on the same molecules with a very different technique. They reached the opposite conclusion as us in their case. At the suggestion of my chemistry colleague, we had a discussion about this with them once we both submitted our papers. There is some chance that we're both right, since the measurement systems are so different, so when we revised our paper, we allowed for that possibility. Our paper came out very quickly - five months ago. In the meantime, our competitors had a much longer review process (this doesn't necessarily say anything about their paper; review can be extremely variable.). Their paper just came out in a different journal. Not only is their wording much stronger than ours (basically stating that their suggested explanation is the only possible conclusion, period). They don't even reference our work, despite having known about it for several months. Not cool.