My last boat (DCB Mach 26 twin 2.5's) was featured in HotBoat and was on the cover of the 04/00 issue. The boat was tested with 1/2 tanks (50 gallons) and two large males on board. The boat was tested at Havasu with my labbed props that I used on the boat, so I would say that is pretty "real world". The boat radared at 102 and some change. I have driven the same boat to 106 with just my girlfriend and I and light on fuel. I can say that the test they did on my boat was honest in regards to speed and handling.
I have another friend that had his boat tested in HotBoat as well. this was also a Mach 26 with a Teague 740 and bravo drive. The boat radared at 112 and some change. I can tell you that he has run his boat at Havasu at about the same speeds. So in my experience HotBoat has been truthful about speeds. That is my .02