For those interested, I passed 70-457 yesterday, I used Professional Microsoft SQL Server 2012 Administration by WROX, its ok, lots of typos and they often refer to the product as SQL Server 2011(!?!), but it did the job and I'll carry on using it for 70-458. I also had Transcenders but didn't end up using them! For the T-SQL part managed to get by on Beginning T-SQL 2012 by Apress (Second edition), its ok, not as dry as similar books, and books online for the more complicated stuff.
Now, when it comes to 70-458, can anyone tell me if they test you on Multidimensional Analysis Services or Tableau? Or both?