It's very smooth to use, or at least to onboard. Did not try to actually send a message yet, but will try soon. That brings me a bit to maybe my first issue: not really sure how to use it since nobody I know uses it yet. I'd be ok with some way of people to discover me, at least in this early stage where nobody is spamming :-). Also, if I get some people to try it, I'm pretty sure some will raise questions about the privacy of messages, who gets to read them etc. so you might want to look into that (yes, I know it applies to pretty much everything else also).