I'm managing 36 holes of Penncross/Poa (50/50) greens, and I've been using Primo for the past three years. It has helped the putting surfaces considerably.
First, the Penncross and the Poa tend to grow, vertically and laterally, at different rates. This would lead to bumpy and inconsistent surfaces. The growth regulator diminishes this disparity, so I have smoother, more consistent greens.
Adding Proxy to the mix led to further improvement, as the Poa seed heads disappeared, the Poa was even less noticeable, especially concerning ball roll.
I'll try to explain the effect of Primo as I understand it. What it does is it inhibits cell elongation, so the same number of cells are compacted into less area. Thus, you have all the benefits of photsynthisis and respiration in less leaf surface area. This means a denser and lower growing sward. What I've found, also, is it means I can mow lower with less stress to the plant, meaning faster speeds without the evil side effects, like thinning, algae and moss being so invasive.
I have seen no bad effects from Primo. One time the sprayer lost a nozzle across a green, and before the operator noticed he had done two passes. This put out a narrow strip of Primo (mixed with some iron and nitrogen) that must have been at least ten times recommended rate. The only result was that those stripes were dark green for about 3 months. This was on Poa, too, so I don't know where people get that it's hard on Poa.
I don't know that Primo has much effect on fertilizer, chemical, and water usage. It seems to me that it would be a benefit regardless if you were on high N, low water, or any combination.