Please see the relevant entry in the FAQ.
I take an admittedly conservative position because the most important thing is to keep the integrity of your photographic data fully intact under all circumstances.
By far my biggest regret ever with the program is when I introduced the feature to automatically rotate JPEG images, after several people asked for it. It was a good feature request and I was happy to implement it. It worked well… until it didn’t, when a bug in jpegtran stripped out the makernote metadata from some images (from Olympus cameras, from memory). Because Rapid Photo Downloader worked on the image being downloaded, and did not create a duplicate before the jpegtran transformation, data was lost. Needless to say, that feature is now removed.
The good news is that so far there are no reports of the kinds of instability that could harm the integrity of the data. When something related to the interprocess communication code (powered by ZeroMQ) crashes, so far it has done so abruptly, which is much better than silent corruption.