You may want to read some of the experiences of 2011 buyers who are having problems with the 4-cyl engine making noises at startup and stalling. Check out the Edmunds town hall messages.
GM has not been so good about getting a solid fix for the 2011′s as best as I can tell from the posts. Maybe they have gotten in front of the issues with the 2012 but I have not been able to find any press releases or statements saying they have. If I had read the Edmunds board before buying my Equinox 3 months ago I would be avoiding the nightmare I am in now.