Schreiner's commentary on Romans is a worthwhile, thorough read. He goes into excruciating details on specific issues, to the tune of 50+ pages on significant Greek parsing issues to make his point.
If you're looking for a commentary, this is one worth reading.
However, I also feel that the reviews for the commentary are a little too glowing. Certainly, from Schreiner's theological perspective (a Southern Baptist, Reformed one), he toes the line quite well. Where the commentary struggles is in interacting and giving fair credence to opposing views. I found that this 2nd edition was often dismissive of other points of view, without adequately interacting with the ideas themselves.
Because of this, the commentary struggles. Schreiner takes as rote that the reader shares the believe in double election (that individuals are both chosen for heaven, and for hell). His unwaivering support for the absolute, unequivocal will of God in the ways of man taints his interaction with the text throughout. I say this not to argue the point -- that is a far greater discussion, but that Schreiner admits there are problems with this view, admits that God may work in other means, but never interacts with those view directly in his commentary itself.
Thus, on key passages, sweeping theological assumptions are made about the interaction between free will and sovereignty. Even when parsing Greek, Schreiner's assumptions often guide his interpretation, without thoroughly interacting with opposing views. Major treatise and academic scholarship are dismissed in brackets where he states who he agrees and disagrees with, without explaining why.
All that to be said, the commentary is solid, but go in with your eyes wide open. This is not a neutral stance, but a defence of a single perspective without interaction. It is not uncommon for the author to accuse others of some overlook or bias in their theology, only to engage in the same behaviour within 50 pages.
Foundational for understanding of Romans. A worthwhile read. Great for developing your own bibliography on academic issues in Romans. Use it as a primer, then explore the issues yourself to draw your own conclusions.