He's been poor in defence, and just average in attack... He's certainly not providing enough 'bang for the bucks' considering he's one of the top earners.
One of the glaring things I've noticed is that he seems reluctant to take on the line, particularly from kick returns or from dummy half. In superleague he ripped defences apart with kick returns, and with scoots following quick play the balls, but he's just shovelling the ball on at the moment in these situations for the Warriors. Add to that, the fact that the 'out the back' play that made him so successful at Wigan is easily defended in the NRL, and that explains why he's struggling in attack.
The defences are far too organised and good in the NRL for him at the moment. In superleague, a wirey, quick and deceptively strong runner playing in a dominating team is too much for the defences to handle, in the NRL that's simply not enough - plus the Warriors are far from dominating.
Hopefully he'll continue to learn and get better and grow the confidence to back himself and take on the defences more - I'm not sure his strengths will be enough though - to be a top fullback in the NRL, you need to be much more than just a decent runner.
In defence, he's a mile away from being even average - he needs to start putting his body on the line, at least he'd get some respect for making the effort, at times he's looked as though he's scared to tackle some of the big boys.
Also, where's his attitude gone? He was a bit abrasive in SL, and was happy to dish out verbals and niggle - he looks intimidated in the NRL.