Of course there are going to be bugs, the Jolla device/SailfishOS combination is in beta phase. I am even collecting a bug list here so the glitches can be collected and solved easier.

However, what I have not yet once encountered is spontaneous crashes/boots. I do not understand where you get those from

About the UI concept; I use N9/Harmattan extensively, as it was my only mobile OS for 2 years before Jolla, and I find the Sailfish gestures very familiar, an extension of what I have been using all the time. The UI is very easy to use and adapt to, and really natural for me.