Originally designed by people to provide Overloud Scarbee electric pianos an effects section, the software is ironed in the bosom of Overloud since the purchase of Scarbee by Native Instruments. Like all plugs from the publisher, it is 64 bit, VST / AU for Mac or PC with a doc almost useless as the plug is easy to use.
I use Studio One in Cubase 2.5 and 6.5, in the context of Scarbee pianos in Kontakt. It works impeccable.
I've used it for over a year and I do not see what I could say negative: all sections can be chained in the order you want and effects arsenal covers all my needs: tremolo, chorus, flanger, flanger, overdrive, auto wah, compressor, delay, etc.. Whether with Rhodes, Wurlitzer or Clavinet, it works perfectly with that and I know it works very well with other virtual electric piano. I confess myself never fun to use on other sources than these, but I guess it can also be very interesting.
Obviously, as suggested by the vintage in its name, the plug focuses on traditional effects: it does not replace a Warmverb a Effectrix a Tornado or a CamelSpace for delusions oriented Sound Design.
Only lacks the rigor that section simulation HP convolution which would be consistent with the whole. And perhaps a section 'Lo-Fi' too. But these tools are available in other plugs, this is not very annoying ...