Join Date: Feb 1999
Location: San Jose, California, USA
Programs: AS 100K, UA MM, AA MM, IC Plat Amb, Marriott Gold, Hilton Gold, Hyatt Explorist
Posts: 3,146
As with most issues like this, the FAs have a lot to do and probably use a very simple test to determine if a personal electronic device is allowed. My guess: If the FA sees a physical keyboard, the FA will assume that it is a laptop and thus not allowed; if not, the FA will assume that it is a tablet and will allow it. I doubt the size (within reason) will have anything to do with this determination.
I just purchased a smallish (10") Windows transformer (basically a tablet with a keyboard dock), and despite its small size and a combined (with keyboard) weight less than that of many tablets, during takeoff I plan to use it without the keyboard just to avoid any issues.