I'm a sandwich Calvinist.
For sure, Calvin's commentary on Romans is instructive. I learned quite a bit from one of history's greatest minds. I don’t think he makes his case on many of the "points of Calvinism", but this is mostly due to the theological progress we've made over the last 500 years. Here's where I differ:
I can go along with Total depravity. I don’t think people are as bad as they can get, but I do agree that there is nothing in us that merits salvation.
I also don't buy Unconditional election, one of the more famous elements of Calvinism. I think Molinism as advanced by William Lane Craig (see my review of his book The Only Wise God for more details) accounts nicely for passages like Romans 9 and Ephesians 1 without having to do acrobats around passages where God holds people responsible for their actions or invites them to salvation.
Further, I don't agree with Calvin's teaching on a Limited atonement. While I haven’t explored this as much as some of the other doctrines, it seems to me that Christ's blood is sufficient for everyone.
Again, I need more convincing that grace is Irresistible. Can we really not deny the calling to salvation? Meaning, everyone who is offered salvation will necessarily accept? I realize that Calvinists side-step difficult passages like 2Peter 3:9 by dividing God's grace into two parts: common grace which is enjoyed by all, and special grace only recieved by the elect. Kinda makes the teaching fool proof. You can always say the recipient had only common grace if things don't work out.
So I guess I'm a sandwich Calvinist, because I do believe in Perseverance of the saints. So, I'll go along with the first and final points of Calvinism, the two hills of the loaf. Also, roast beef is delicious.