He was always a bit of a tweener. He isn't a speed rush guy at 300 Lbs., but he isn't really big enough to play inside full time. The truth is he is more of a 3-4 DE that can penetrate. It makes sense using him inside on passing downs because he can push the pocket when he doesn't have to worry about the run against an OG or C. And on normal downs he can get decent push and the occasional effort sack (when he cares enough) all while being very good at setting the edge and playing the run. The problem is that he is kind of a one trick pony in pass rushing. He either wins with power and effort or he gets stuffed.
But, like Buzd said, we still need an outside speed rusher. Kikaha is a nice player, but most of his pressures and sacks come on effort and cleaning up when the play breaks down. That's a great guy to have, but he's not going to go one on one with only 4 people rushing and blow past a LT or RT for a sack very often.