Im always skeptical, im even skeptical of buying a Blu-ray or 3D Blu-ray.
These are the steps i take as a consumer before buying a Blu-ray:
1) Is it a good movie? (if i dont know ill watch the trailer, watch the movie on YouTube or illegal download it and watch a few scenes to see if its any good to buy on Blu-ray and delete illegal DL)
2) Does it have great scenes in it that really would look amazing on Blu-ray scenes that really pop out visually? (thinking about spectacular action scenes or a scene with a beautiful environment)
3) If its a old movie i really liked and it just came out on Blu-ray i tend to buy it pretty fast, but if mostly wait a while if the price lowers and then buy it

or at a high porice if i really want it ofcourse.
4) If i see a cheap Blu-ray for €5 i tend to buy it. also cheap but great title movies when they do discounts on them.
I havent bought any 3D movies because we dont own a 3D projector or TV, im gonna wait till 2012 because i want them to fix those shutter glasses or having not to wear any glasses for 3D, when it stops ill buy a 3D tv/projector.
But these are the steps i would take before buying a 3D Blu-ray:
1) Good movie? did i enjoy it?
2) Any great visual scenes in it?
3) Did they filmed it with 3D camera's or did they converted it later? (if converted afterwards, no buy + i also dont watch converted 3D movies in the cinema, i did only with one "Bloody Valentine 3D" SUCKED! never again.)
4) How much for it?
Most of all the Blu-rays i own are great action movies and the rest are in general great movies not visually but just great movies.
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