I import STEP files from Asian suppliers all the time and, although I can't claim it is a trouble free process, it usually goes fairly well. I am still running 2010, but I haven't heard that any other people are reporting problems in 2011 or 2012.
Any version that you use, make sure it has the latest patch.
SW2011 x64 SP5.0 works well for me when I receive a lot of of files from Asian suppliers/costumers/clients.
Do not upgrade to SW2012 x64 vanilla if you don't know the vanilla details.
Vanilla version usually have lots of new bugs.
The path and the file name should be in englisch. In my case the folder name was in cyrillic and i wasn't able to open the file until i change the folder name.