I too am frustrated about this since the only reason I am buying a tablet is for mobile credit card processing.  The Square would not be my choice since there are better services out there but I cannot find any information that the Nexus 7 will take the reader for Roampay or Gopay either although both do have apps.  The Samsung Galaxy will accept both readers.  Am very disappointed since the Nexus 7 is my first choice over the Samsung.