I too was selected for testing, (I have 6 x very large trees), but coincidentally as soon as I started to comment on sites such as this, every time I logged on to test, I was reminded of BETA TEST - Confidentiality Agreement! They obviously don't want people like me voicing my concerns.
My testing was obviously not as successful as yours.
My syncing did not bring my images & media over; I had to resurrect data using backup files, this resulted in duplicated trees & unlinked/break in sync.
My main concern was the quality of their support service. No phone - just online. Poor quality & Varying advice depending on who you hit on.