I haven't bought many Blus from Region A yet (only if it isn't available as Region B). When I do, I look on
this site, if it's region free. Or I look in the contribution notes of the DVD Profiler profile, if someone has confirmed it as region free.
Though this region restriction isn't currently much of a problem for me. As far as I can see, Blu-rays are currently cheapest in the UK, which is also Region B. Most of my Blus are bought there.
A lot of Blu-ray players can be made region free for DVDs, but not for Blu-ray. Mine cannot be made region free for either (though they say, that the Australian model can be made region free for DVDs).