Will we be perfect in Heaven? I think most (if not all) Christians would agree that there will be no sin in heaven. However, we often make mistakes that aren't sinful: accidentally spilling a glass of milk isn't a sin. We don't know everything, we aren't all virtuosos, nor are we all Olympic athletes, but ignorance and a lack of skill and athleticism aren't sins either.

So: will we be perfect in Heaven, mentally and physically?
Only God is perfect, and (except for Mormon teaching) we will never be God. Ergo, we will never be perfect. 

Going a bit deeper into the word, however, when the Bible uses the word perfect, it is typically the Greek word telos. Telos does not imply a state of being, but rather a direction toward the end for which a thing is made. It has the sense of a target, minus the actual arrival. 



Note: This doesn't mean our bodies won't be a heck of a lot better - our new bodies will be glorified.  That which was sown perishable is raised unperishable.  Our bodies will not be affected by sin, and that makes them way better than we can imagine now.

But perfect is a different level entirely.

Think of it as two ants and looking at my belly and saying "Its the largest thing ever!"  No, it's pretty massive, but there are larger things. (Until I eat them)