I've picked this back up recently. I fought what I presume is meant to be the 'dummy' final boss for a pretty unrewarding time, and had to resort to a walkthrough to find out what I'm meant to be doing next.
It's fun enough, but I'd pretty much echo what Kriken said on the last page: it's a pretty good Metroidvania, but it is just another Metroidvania. It doesn't feel special really. Also, the long loading screens make navigation just a bit more frustrating than it should be. I'm still enjoying it though, and will likely go on to fight the 'proper' final boss assuming the game doesn't pull any horrible tricks (besides the one Andy told me about).