Hi Gary,
My Hollowmasters are my favorite tools. I've use a variety of other hollowing systems and just like the feel of them. I also disagree about the round tip. If you flip it, you have the round side of the tool against the rest and can shear scrape easilly. Also, I use it as my primary hollowing bit and don't use the straight bit much at all.
As noted above, the depth of hollowing is quite limited, with the big tool doing about 9" at best and the smaller most useful for 6" or less. Within this range, however, they've got a great feel.
Notably, when you're using the larger, gooseneck tool you have to be very careful. If you brace the tool on the curved part you lose all of your torque advantage and become instantly very unstable. If you move the rest back so that you're bracing on the straight section, this improves.
Finally, a couple of hints. First, always set the tool rest as high as you comfortably can and still get inside easilly. This lets you lever the cutting bit upwards into the wood and gives you lots more control and reduces vibration(if it catches, it automatically disengages). Second, ditch the stock handles and turn yourself some nice, extra-long handles to give you better leverage when you're extended way out. Finally, start with the smaller, straight one rather than the larger gooseneck. Easier to learn with and the gooseneck isn't needed till you're doing large vases with wide shoulders.
Great, versitile tool.
Dietrich