If people want to try Niacin for the purported health benefits then they should only be taking Nicotinic acid (causes flush) and not Nicotinamide (doesn't cause flush).
The bulk of the research on 'niacin', to my knowledge, has been done on Nicotinic acid, which is a completely different chemical to the more popular (on amazon etc) Nicotinamide. The reason nicotinamide does not cause a flush is because it is quite simply not the same and doesn't cause the same effects.
I tried Niacin (Nicotinic acid) about two years back, at doses of 500mg. The flush comes on within an hour or less and the intensity and onset seems very directly related to the contents of your stomach. I find it quite pleasant, and it's kind of like taking chillies but more intense. The flush starts in your head, shoulders, chest etc, then works its way to your extremities, lasting about one hour. It is characterised by going BRIGHT red (seriously, if somebody saw you in public they'd be very concerned) and sort of intensely tingling and itching.
I did feel that it helped with anxiety/depression, and often after the flush had subsided I would feel a sort of light glow.
I'm trying it again in a few weeks and will report back.
But again, trying to avoid the flush is ridiculous. It's like trying to take a form of LSD that has no visuals and introspective thoughts or something. That just wouldn't be LSD.
(I've been meaning to post this in here for absolutely ages).