What is going on: why do so many reviews of Aperture say "it does not work"?

[xxmarkc]

Aperture is on my list of possible buys. Only delayed since I have not yet migrated from PC+Picasa.

Every time I go to the app store and read reviews they are either "it is great" or "it does not work at all".

There must be a simple explanation for this:

1) The software is crap and roll a dice to find out if it will work on your PC (I find this hard to believe).

2) Pilot error. There problem is the user - they don't know what they are doing.

3) Old hardware / software. I have a 2011 iMac (around 10 months old) and always run the latest os)

4) Something else?

What do people reckon?