Close button sends client to the tray, statically linked Qt for OSX.
See the Changelog for list of features and fixes currently only available in the nightly builds.
Most of the improvements in tonight's build, a few days overdue after I lost my Mac and Linux virtual machines to some indiscriminate deleting and having had to rebuild them from scratch, are to do with the file transfers view. The first thing you might notice are progress bars, a decidedly nicer way to present each transfer's progress. This change is more than cosmetic however; You will also notice a separate progress bar for the total of your downloads from each user, and even additional progress bars for each folder, if more than one folder is being downloaded from a particular user! Wow. An additional column in each transfer list now also shows the estimated arrival time for each download, and once more, an ETA is provided for all files from each user, and per folder using the same logic as with progress bars (i.e. you'll generally only see an ETA next to a progress bar).
Finally, aggregate file transfer statuses are now only shown per folder and user if their tree node is collapsed. And oh, I almost forgot, both download and upload views now feature expand and collapse buttons to expand and collapse all users and folders in each list. I'm sure there are many corner cases with all of the above that aren't being handled absolutely perfectly yet, and there may be some other more glaring problems I haven't run into. Fixes are sure to follow in any such case.
Actually, the first thing you'll probably notice are the different colors to correspond with different transfer statuses.
Other, non-file transfer list related changes include:
Windows, Mac and Linux versions on the download page.