For those worried about slowdowns over the life of the device and TRIM support. See below from Anandtech.
The new Nexus 7 (2013) with Android 4.3 includes support for fstrim, essentially idle garbage collection, which TRIMs the eMMC when a few conditions are met the device is idle, screen off, and battery above roughly 70-percent. Im told that TRIM support has been part of the eMMC standard since around version 4.2, it was just a matter of enabling it in software. The result is that the new Nexus 7 shouldnt have these aging affects at all. Better yet, fstrim support has also been added to the old Nexus 7 with as of the Android 4.3 update, so if youve got a Nexus 7 that feels slow, I/O performance should get better after fstrim runs in the background.