Many thanks for the feedback everyone.
Turns out this is the ugly part of game dev, hopefully pumping up the system requirements and some proper error handling, will make people aware of what they need.
I'm targeting people with decent computers, something that can render 3D graphics with post processing at a playable fps, I really REALLY want to avoid the old pipeline, it's just seems dirty, do some newer AAA games even use old pipeline these day?
For example I am interested to know what versions of OGL do Valve use for their games on MAC?
And I'll probably just end up going with 3.2. seems to be a better choice.