I have been a user of Newgenlib. Both commercial and open source. When I was working for BLDEA, we procured the system for 15 colleges of the association. Right now I am using the OpenSource version.
As commercial users we paid our AMCs promptly at the beginning of the stipulated time. Verus Solutions turn around time to solve any issue was less than an hour. For any bug fixes they took 24 hours to give a new build. We were very happy with their service.
As an open source user also despite not paying a penny to them I got support through their open forums. I am using their system smoothly. I helped nearly 15 libraries use newgenlib open source. I know more than 60 libraries in this region using newgenlib open source. For many libraries it has become a boon.
However my request to both these organizations is to conduct more opensource workshops. This will help our community a lot.