Being wary that something can 'bite' says to me that a pilot has not reached a sufficient level to be able to control or understand their machine properly. The handling notes and experience of others should allow you to see what the envelope and limitations are. Step outside it and the a/c will 'bite', but it is you who provoked it. If you know the a/c well enough and the issues surrounding it, then hopefully you are less likely to get into trouble because of a handling error…. You shouldn't need to be 'worried' about any a/c you fly.
Well, the Harvard is only type mentioned in this thread that I have personally flown. And indeed, as someone with less than 20 hours in the airplane, I am 'wary', even 'worried', when I fly it. I completed a four day ground school and received excellent instruction from three experienced ex-military pilots, but I am still very conscious of the fact that it is a demanding aircraft that can quickly get a pilot into trouble.
If I correctly understand SASlowly, his point is that any properly trained and experienced pilot [which he believes is the only sort that should ever fly an ex-military type] will be completely familiar with the aircraft and will be entirely confident in his or her abilities. I don't know anything about jets, but it's well-documented that many high-time combat veterans were killed in Harvards during WWII ("it's just a trainer"). Even Chuck Yeager was recently humbled (see
NTSB and
AvWeb reports.