This feature is extra-cool, btw. I have a new workflow here at work that's going to have me using this whereas I haven't in the past. I used it for the first time tonight to syncronize some files on my local hard disk to a folder on the destination system's drive over a network.
I noticed a quirk I thought I"d bring up. I'm in the middle of heading out the door and knew I'd forget tomorrow so sorry if this already exists, I noticed the source and destination folders had swapped themselves when it was done with the process. The source was the destination folder and vice-versa. I confirmed that it didn't syncronize this way, it must be a display issue or maybe the syncronize button is activated after it's complete or something. I don't know if this is a common occurence but I noticed it tonight. I can try and give a detail on the steps I took to get it that way if it's necessary, hopefully you can tell just by looking at it where to fix it.
The Source & Destination fields in the Synchronize panel are usually "locked" to follow the source & destination file displays. (You can "unlock" them by clicking padlock icons to the right of the two fields.)
This means that when you change directories in the file displays it is automatically reflected in the Source & Destination fields.
But what it also means is that if you click on the destination file display, which will make it the source, then the Source & Destination fields swap over.
Which filesystems are the source and destination using?
Different filesystems (e.g. NTFS, FAT32, FTP sites, network drives, Zip files) all have different time resolution for different timestamps. Some can only count time in two-second intervals, for example, so times will be rounded up or down when you copy files to them.
The "ignore seconds" option exists to combat this problem.