Don't think he looks good enough going forward. Young looked better on the right today for instance. Obviously harsh to judge but he didn't exactly pull up great attacking numbers for Southampton in his 2 seasons. A United full back/wing back will need to offer more than just defensive solidity.
Is it really fair to judge him on numbers? Prior to the last two seasons Evra's numbers were very low but his build-up and link-up play was so important to us. Shaw's good at that stuff too. Not as good though and I don't think he's a wingback at all. More suited to the left-sided centre back in a back 5 I reckon. He's definitely got the skillset to be an influential attacking fullback for us though.
At the moment he's clearly playing within himself because he's adapting to a new team, in a new system, quite possibly in a country (and more importantly, a climate) he's never played in before all the while trying to get to know his (much more successful and experienced) team-mates and manager. It takes a while to get it together for most people.
Everyone remembers Evra's shambles of a performance against Trevor Sinclair where he was torn to pieces defensively, but he wasn't that great going forward to begin with either. In fact the few times he was played further forward as a LM he looked pretty inept in attack. It's much easier being a threat going forward with someone in front of you occupying the fullback and creating space for you to gallop into.
By the way, for anyone ready to jump on the "another overhyped English youngster" line, I was watching the match with Italian commentators and they called him a great fullback.