In other forums a lot of wedding photographers and working press who use them to fill in afternoon light (something that would tax them quite a bit) complain loudly and often, especially those who use them with a lot of rapid fire shooting.
While the ratings at B&H are high, the "Lowest Ratings" consistently harp on overheating issues. (I don't know if I can refer a link to that or not so I won't.) :-)
Since I've already upgraded firmware and use the Sanyo batteries, and I might try to turn off the Thermal Cut-Out (although that sounds wacky).
As for sending things to Nikon... I have a genuine love/hate affair with Nikon repair/support well earned with over 40 years of use. They have treated me very well and very badly. I've sent them things very broken and got them back in very good condition, and I've sent them things not broken at all and paid very dearly to have them returned with with absolutely nothing done.
My guess is that they aren't going to buy into this one. If it were to be a firmware fix, it would be released by now. It's likely a much bigger fix they don't want to get into.
If some folks aren't taxing their systems, Nikon might let the sleeping dogs lie.
But I suspicion that if I send the unit to Nikon all I would accomplish is paying more money out. Nikon repair is going to let me know (after $90-125) that it is up to spec. Like I said. I have SB800's what I bought the SB900's for (that's the rub), and the caution for someone who's interested in a flash for that type of work. (And the reason for my curiosity for whether or not the SB700 will have a Master mode option, which it doesn't seem to have.) ;-(
There is also some skinny about different modes possibly more juice and heat to the unit, Rear Sync is more than front curtain sync and so on, I forget the order of things. I don't know how accurate that is or if there is any truth to it at all.
The Metz Metabeltz units look great and seem to be completely compatible, but their recycling times is bleak without their pricey battery pack, and that's an accessory I don't want to tote.