Its becoming pretty clear that the Preview Grid is not working as a viable platform for exercising and validating the patches prior to release.
A couple of suggestions:
#1 Pay a good bounty in L$ to an account in the main grid during certain "Load Testing Windows" just for logging onto the Preview Grid and not going AFK (kind of like an internal "all hands test" window but for all residents). Pay something significantly better than the camping rate on the main grid and announce the testing windows all over the place.
The effect of this is to get a bunch of people logged onto the preview grid so LL can get a real load test and see the effects of a lot more people on the servers. Hopefully the campers coming over will also take note of some of the UI changes and give feedback along the way.
#2 Pay a significant bounty in L$ on the main grid for being the first to report a verified bug on the preview grid and double it for bugs reported during the "Load Testing Window". Also pay 10x or 100x for submitting a verified exploit (based on the severity of the exploit).
I think a big incentive to come test, especially during a test window is needed. Its obvious LL does not have the QA resources it needs so (since you are now printing money) why not earmark a big chunk of L$ for testing bounties? I would hope you could pay out enough that a testing economy could rise that would pounce on these releases as you load them and race to log bugs and exploits.