I have used the Wugfresh NRT 1.6.6 on my Nexus 7 2013 and achieved root without issues. Be aware that more user interaction is required with this Toolkit than previous version, which may be isolated to Android 4.3. If you are new to rooting, then give me a day or two and we will have a step by step guide. The first step of unlocking the bootloader will delete all programs and data from your tablet, so if you may want to use the backup feature in the toolkit before rooting.