More a case that Anderson doesn't have a glaring weakness against spin. He looked classy in Bangladesh; not KW/TPC/Michael Clarke levels of gun-ness against spin, but he's definitely well above the median. That said, 'hopelessly inept' is more-or-less the median these days.Is he? I have been out of NZ for a while now so I haven't been watching domestic cricket but New Zealand wickets are hardly spin friendly and the quality of domestic spinners judging by who we pick to play internationals is poor. He looked all at sea with the ball turning against quality spinners, then again coming in with 3 overs left needed 18 an over is tough for anyone, Pollard also struggled. Personally if Hussey has another shocker I would be tempted to drop him and try Anderson as an opener and bring in Santokie.
As hendrix says, he doesn't quite have the technique to deal with the ball outside off stump, doubly so if its moving around a bit. From what I've gathered, driving on the up, in particular, is not a strength. Incredibly talented guy though. Very good young cricketer - he's smart enough to minimise how much a bowler can take advantage of his weakness; knows and accepts he has limitations at present.
Him as an opener would be suicidally bad thinking. You sign Todd Astle for that purpose. And let's remember that Hussey has no cricket behind him since the end of the BBL. Give him a couple of games and he'll be right - form is temporary, class is permanent (until your eyes go) and all that.