I've heard it and think it is a great sounding amp and a really solid value for what you get. Primare is one of the few who seems to be doing their own design rather than just repackaging an IcePower/Hypex/Pascal module and calling it their own.
A friend uses a pair of the A35.2 amps in mono mode, it sounds great to my ears. I haven't heard his system running just one of them though so I can't say how much it improves things. Probably depends on your speakers and how difficult they are to drive, to a large extent.
I would call the Primare sound a bit on the cooler side, but no more than many of the IcePower or Pascal class D amps out there. With proper component matching you can really get an excellent result with the A35.2 for a relatively small expenditure.