I know a lot of users were alienated by broken promises associated with folder limits the free version. They eventually walked that back, which took guts. I have never needed to sync more than 10 folders, so it didn't affect me in a practical sense, but it was an ugly situation.
As for encryption, we know they know how to do it, because they grew out of BitTorrent. I think the idea that they might not be doing it properly with BTSync is a bit silly.
I've been on and off with BTSync since version 1.2, and it's been a bumpy ride for sure. I tried every alternative I could find, including Syncthing, and ran with AeroFS for a while. In the end I came back to BTSync because it's the only thing that handles my use case properly (mostly idle, with occasional surges of many thousands of small files all being changed within a very short time interval) without choking, and with reasonable resource usage. It's been solid and reliable for me for over a year now, and it forms an important part of our workflow.
So yes, I feel a bit defensive about BTSync, but have no axe to grind against any alternative that works properly for others.