We won't really know how good Widdopp is until he has a run in the side without one of Cronk/Slater. The Storm use a lot of set plays, which generally use others to make the key run/pass/kick. Widdopp primarily plays the link man role, although when it IS his responsibility to make the big pass he does it well. IMO the Storm could be even more dangerous if they allowed him to have a couple more plays to run, using Slater as a decoy.
He's also got a full back's view of defence on the line, and often acts as a sweeper.
Its funny how bias can be involved in perceptions. The Storm blew a clear try yesterday on the back of a Widdopp break when he didn't pass to an unmarked Slater on the inside. The commentators immediately started almost joking about how badly he'd done, until it was pointed out that the supporting Slater had clearly overrun him - any pass would have been a mile forward.