First off, I just want to say that you are a very talented artist. Your realism is wonderful.
You did a great job on this protrait. The proportions are correct and so is the perspective. There is a strong sense of dimensionality and that's great because there's nothing worse than when your picture feels flat (unintentionally).
There was something that seemed a little off when I saw this the first time, so I googled some images of Pattinson and finally put my finger on it. I think his lips are just a tad fuller in your drawing than they are on real life. They are wonderfully shaded though. His squinty eyes and crazy eyebrows are so spot on.
The amount of detail in this is amazing, but if I had to pick an area to work on based off this piece I would say the hair/ear. They just seem like they were a little rushed or didn't receive as much attention compared to the rest. The hair doesn't seem to blend and flow like actual hair would.
Having said all that, this portrait really is exceptional. Again, you are very talented. I know this was a little long-winded, but I hope this helped!