Where GSP gets in trouble is when his opponents get in tight and are able to exchange with him close.
He is at his most effective when he is able to use his gorilla reach and really extends his punches, see the Hieron, Hughes 2, parts of Sherk and Penn fights.
But, go back and watch the Sherk fight again and although Rogan and Goldie only acknowledged GSP's shots landing, Sherk was imo winning many of the exchanges.
It just seems that GSPs build does not allow him to have the hand speed close. We also see this in the Serra fight.
George is not gun shy in the slightest and seems to like mixing it up close at times, but he will continue to have trouble with many of his peers if he continues to do this.
Dancing around, peppering kicks, jabs, and long straight rights is how he needs to always strike to be dominant imo
Just an observation