When you get the Transformer, you might find that the supplied USB <-> proprietory connector lead is a little bit too short for some things, for example browsing whilst charging up the unit. I had some decent USB extension leads already so I thought I would use one of them. But I tried three different USB extension leads all which refused to charge up the unit, when connected to the supplied power supply. Browsing around the Web on some forum (I cannot currently remember which), I learned about this:
CPO 2M USB 3.0 Extension Cable, Male to Female - Black and Blue
I bought one, and can verify that it works perfectly, allowing a significantly longer charging lead from the supplied Asus PSU, to the Asus tablet. I guess it must be something to do with USB 3 specfications as all my USB 2 extension leads won't allow charging for some odd reason.
I hope others find this information useful.