It looks nice, but the installation experience is (was?) terrible (as in - didn't work at all). Note the long gap between the 0.5.6 release (January) and the 0.6.0 release (July)? There were 3 (4?) Spark releases in that time, and that meant that none of the out-of-the-box released worked for anything except the version of Spark you downloaded with it (and from memory that had problems too)
I got it working and evaluated it in some depth. I'm from a Java background, so I really wanted to like it.
But it turns out that all those features that seem really nice are mostly only nice if you are trying to build applications, not notebooks. Maybe it has improved, and maybe for some usecases it makes sense.
Thanks for honest feedback (although it sounds bitter) - we are working hard on improving situation with release schedule indeed.
If there is any chance you could elaborate on installation experience though a JIRA issue [1] - that would be very much appreciated.