I submit to MDPI two years ago – and since then I told myself I will not repeat it again. Everything was OK – the journal was brand new, without an IF and of course with the appealing waiver of publicaton fees for the first year of the existence of the journal. My editor was a Chinese (I will not reveal his name unless someone want this), who was very kind and welcoming at the point of acceptance of our paper. We had our paper formally accepted but after we refused to pay 200 Euros for proofread to a company of their choice we were rejected straight away. Of course our work got published where it deserved but ever since I ask myself what is the OpenAccess all about? If it is only about making profits from authors, then it has to be made clear so anyone who want to get into the trap – to get with the conscious that this his/her choice.
P.S. The issue with MDPI is the poisonous mix of quality papers published by them, good looking and sophisticated publication system, and of course luring offers such as publication fee waivers etc., which at the end are just not true.