Craig Keener recently completed a commentary on Acts that's several thousand pages long. It's not out yet, but Keener can be considered highly knowledgeable about Acts and scholarship on the book, given the work he's recently done while producing such a large commentary. Michael Licona mentions a significant piece of information about the authorship of Acts, which Keener gave him:
"Perhaps one half or more of modern English-speaking commentators on Acts maintain that Luke was a traveling companion of Paul." (The Resurrection Of Jesus [Downers Grove, Illinois: InterVarsity Press, 2010], p. 382)
Given how non-conservative modern scholarship is, and given how skeptics often react to the suggestion of authorship of Acts by a companion of Paul, I think a scholarly acceptance of 50% or more is significantly good.