…errrrrrrrr… a 'little problem' in making a proper user interface?
Why is the very normal one of FTP so familiar and this… probably copied by an Ancient Egypt pyramid internal wall.
Funny, absolutely agree, transgressive, ironic (in fact VERY ironic!) but I'm an old fashioned man and prefer to stay on my familiar, used, beloved, trusted aqua interface…

There are only two problems that I would see solved in a next release:
- after installing, as you can read in the troubleshootings, you can't see the preference pane. (don't fall in panic, simply restart system preferences).
- if your Mac has only one fan, it can't recognise it and SCARES YOU by telling that the second fan is down, so… why not doing something to eliminate this anxiogenic false information?

Let's be helpful and underline the weeak points.
I tried this on the very little library on my MBAir, results:
-6 duplicates, in detail:
-the first 3 were two different versions 29 seconds different (same title and author) and, even worst, one was a VIDEO!, so they're not a real duplicate.
- the last 3 were the video and the pure audio version, same time, this time, nevertheless not reason enough to consider them 'duplicates'.
I already used other duplicate finder apps and I deleted unfortunately some duplicate, yes, but of a corrupted file (the ones who can't be played till the end and let iTunes jump to the next one, another very annoying still not solved problem of iTunes!).
Before to consider 'duplicate' a file, it should be deeply analyzed, if not, it should be named 'similar' and, possibly, listed IN WHAT they differs and in what they're IDENTICAL.
Tags and slightly different names or infos could result in a slightly different size of the whole file while the content is identical, in this case list as identical file with different attachments.
Shortly, this program still needs a heap of work to match the real needs of the rest of us, even more if we have to work on a real LIBRARY of tenth of thousands of files or more!

Already the fact that Skype's new version pop up alert has a button pretending to send you to a 'what's new' page which NOT EXIST is a sign of a deep cheater's attitude!
Beside the kid's interface, I never understood why they deleted the history feature and will not consider the 5 version as professional as the 2.8 till they can reintroduce it also in this absolutely not needed 'upgrade to 5'.
I suggest Skype to keep evolving the 2.8 for serious uses (call it Skype Pro 2.9) and Ok, insist to give this funny toy to the beginner customers, the ones who also likes msn!!!!!

I have a little question (by time!):
"Can I be sure that the resulting file is the smallest 'lossless' that I can have starting by the .flv file?"
Get Tube downloads whatever at 192 kB/", a bit optimistic, perhaps, other at 64 the same file…
This of the 'minimum LOSSLESS conversion is an unanswered issue also for .jpg and .mp4 files by YEARS!

Even the good freeware alternatives are working even outside the country of the developer, THIS NOT! Sorry to be so frank, but it's A SHAME!
Hard to give 'a rating' of 'features, stability and ease of use' a product that I can't evaluate (this is why I miss so much Version Tracker!) and sorry to have been forced by this site to do it.
BUT… let YOU ME finally try it (means make it WORK, damn!) and I promise indulgence!