OK, I cheated. Waited patiently for it to be pushed and finally went and did the Google Services Framework thing -
http://forums.androidcentral.com/google-nexus-7-tablet-2012/300186-force-4-3-ota.html
Took several tries but the update finally showed up. Installed without issue. I did have to do the 'fix' (as reported elsewhere) for Google Store as updates weren't working - so that was remove my Google account and then sign back on, 'Adding' a new account. Google Play and all Google Account sync then refreshed without a problem, though I had to renew my own preferences there in Accounts (no Google Photos).
All seems fine - not seeing anything huge yet, but time and experience will show the 'improvements'?
EDIT: Only obvious hiccup so far as been that my
MX Player PRO won't run. Put it to one side until it gets updated and downloaded the
VLC Player Beta, which seems to work fine. Meanwhile, I picked up the new
Permissions Manager app (accesses a hidden feature in 4.3) and have been turning off access to areas other apps have no real need to use as far as I can tell. Even if it says it hasn't done so - yet.