Peter seems to have been greatly affected personally by Ernie Brooks's fatal crash. He searched hard for a technical explanation for an event that was probably a porpoising or zero G accident of the type that was all too common in Bensen-clone gyros back then.
I flew my first 100-150 hours with a spindle head, liked it and experienced no weirdness such as Peter predicts. I liked the gimbal head less, in fact, when I first got one. The gimbal head made the stick feel like it was planted in a pail of oatmeal. The spindle head had what was to me an enjoyably light stick force. I didn't fly over 70 mph and didn't try aerobatics, though.
(BTW, the only reason I bought a gimbal head at all was that the spindle in the Bensen spindle head is a little suspect from the structural viewpoint. I had mine magnafluxed a couple times because it worried me (a few did break in flight, with obvious consequences). The spindle was made by cutting various journal diameters into bar stock on a lathe. This is a bit like cutting them into a broom handle; you expose "end grain" at those points where the diameter changes. Shafts like this are better made by forging, since that process makes the grain follow the shape of the piece. The gimbal head uses a dumb old AN bolt as its spindle, and is more wholesome in that regard.)
I never experienced a tendency toward exaggerated flare such as Peter describes. Tipping the spindle aft certainly increases thrust (both lift and drag, more or less in proportion to each other), but the angle between the rotor disk (tip-path plane) and the spindle actually DEcreases when you do this. Why? RRPM increases, which in turn reduces the blowback angle at any given airspeed.