Yes, I have personally known many HIV+ people both before and after diagnosis.
Certainly in the early days of HIV/AIDS, when treatments were limited and prognosis poor, stress was a massive problem for sero-positive people. Apart from the physical effects of both illness and treatment, there was the constant stress associated with the possibility of employment, housing, insurance, medical care being terminated/refused.
Some people I’ve known have been cranky on various drug regimens (side effects are pretty common); some have been cranky during certain periods of illness. A very few have just seemed to be angry at the world in general. These aren’t uncommon reactions to any life-threatening illness, and few diseases have carried with them the additional stigma which has been attached to HIV/AIDS.
While I’ve seen many people make radical changes in their lives following a sero-positive diagnosis, those changes have generally related to focusing on “what’s important”, rather than affecting people’s perception of humanity at large.
In my personal experience, those people who were loving giving people prior to their diagnosis continued to be so after they knew their status, and those who were jerks to begin with remained so until the bitter end.
The one exception I would make to the above statements is that I’ve observed several people suffering serious HIV related neurological complications undergo a personality disintegration similar to that which can occur in people with Alzheimer’s disease. In some cases treatment has controlled the cause and the person’s personality has returned to “normal”; in others, the damage has been permanent as has been the change in personality. Again, this is not unknown in neurological conditions unrelated to HIV.