Those complain is either related to some wish features which is already stated by the author clearly, is not yet included in author webpage. If Author stated clearly before, the potential customer can simply do their "homework" whether this extension suit them or not. the author should not being complained.
Or, more often, other user complain about extension assistance only be given after subscription.
I bought this software and initially just purchase one month subscription. Instead of searching solution forum for days (which I think many user experiences a lot from other commerical extension), I can get the exact answers within one working day, together with enough illustration of graphics aids. You can move on and get your web done quickly.
Guys, it is a very fair deal. Why you use Joomla, it is because you want to set up your website fast.
Is 20 Euro really a big deal to you? Guys, Your time is even more valuable and if you finally find an extension like Datso Gallery and you find it suits your page. Make the subscription now, the author is a man who you can trust on and you will get what you planned to have.