Since being made into a starter, Marcum has pitched very well, giving up 3 or more runs only twice in 10 starts. The only concern is that he does not go very deep into games. Carmona also doesn't go very deep into games, but has been very consistent on the road and is 6-0 with a 1.58 ERA in day games this season. While I don't expect either pitcher to dominate, I also don't see either offense really breaking out against these pitchers. With that view, 9.5 runs is a good value for two solid starters and allows for a lot of winning outcomes.
Running total: +100
It took a subpar performance by Haren, 5 errors, and 2 unearned runs to push the O/U at 8 yesterday. But in the end it was still a push and that is why it was such good value getting the O/U at 8 instead of the usual 7.5 for Haren's starts.