Update: some success, and info for others to perhaps try ...
1. Upgraded my iPad (v2) to iOS 7 - no problems there. Hope was kindled.
2. Tried "reset all settings" approach. This did not seem to work - the typing lag issue showed up as soon as I turned on "docs & data", and again went away when I turned that off. All the inconvenience of rebuilding desired settings, no apparent gain.
3. The interesting bit: while away from home and not on wifi (some idle time to work on the issue), I turned "docs & data" back on. NO KEY BOARD LAG!
My iWork docs synced down slowly over cellular, but did sync. No further keyboard lag issues since (even back in normal home situation - wifi, iTunes on laptop with wifi sync).
I was not as rigorous as necessary in my work to be certain what may have fixed this, and don't know how (and don't want to!) try to replicate the problem.
Open possibilities to consider and explore:
- Wifi vs. cellular ... Problem went away after I turned on "docs &data" on cellular data connection.
= post "reset all settings" ... relevant?
= away from iTunes computer wifi sync ... ?
- Played with settings after reset ... Some other setting interaction? Nothing that seemed obvious to me.
= new iCloud authentication?
- Back-end updates? While there was no new iOS patch, Apple may have made an iCloud change
- iPad iOS update and iCloud touch/sync? May have altered something in iCloud docs or sync states.
Will advise if anything comes to light.
I did call Apple support over the weekend. No solutions, but they did promptly acknowledge the issue, and intelligently discussed known information, options, and workarounds. Overall good support call.
Cheers
W