Every year the Milwaukee Journal-Sentinel has great draft coverage where they directly pull comments from scouts. They mostly have positive things to say about Sanu - he's smart (with a good wonderlic), tough, will do the dirty work etc..., but give him a solid second round grade because of concerns about his athleticism. That unfortunately seems likely given the depth at receiver in this year's draft.
Sanu is ranked 7th among WR prospects, below big time question marks like Alshon Jeffery and Stephen Hill. That seems like a failure of expected value. With Sanu, you know he's going to turn into a Muhsin Muhammad-type who will sting around the NFL forever. A few of these other ones, teams are gambling that they will turn into stars instead of fourth receivers.
Update: here are some more comments in a similar vein.