I'm liking these lubelocker gaskets....
when I installed the cast diff covers last season, I popped in a set of lube locker gaskets rather than doing the RTV thing.
my long term feedback is positive.... on several occasions now, I have come back from wheeling a trip to the rocks only to find a differential drip develop a day or so later. What happens is that I um gently graze rocks with my diffs from time to time and this shifts the cover around slightly. What I find is that a bunch of bolts on one side get loose and then a few on the other side of the cover are very tight.
the cool part is that you don't need to pull the cover or drain the fluid to fix this. You can just loosen all of the bolts enough to shift the cover around with your hand. then just finger tighten all of them and do the two step torque thingy. leak cured!
I did drain and re-use the fresh fluid the last time I did this (yesterday) but don't think you need to unless the fluid needs changing anyway.
anyway, this is a quick fix as compared to pulling the cover completely and then resealing it.
you should definitely still pull the cover and look at your r&p from time to time.