Since you have an '07, you've got a 100k mile warranty. I've read numerous threads on The Diesel Place about whether or not to run a DEX VI during warranty. For me, I only got 36k miles of warranty with my '06, so I'll be out of warranty in another year or so. For you, that's a lot longer time to run DEX VI. I belive that DEX VI is a much improved product over the previous generations, but probably still not as robust as TranSynd or Torque-Drive or the 204SAT.
After talking with a couple of guys that actually work at different Allison dealer/service centers, they agree that they are not allowed to work on a GM truck up to model size 3500 (commonly called a 1-ton) until the GM warranty is expired because they do not get reimbursed for it. That's GM's way of protecting the GM dealers that sell the trucks. After warranty, Allison will work on your 1000 series transmission, but it will cost out of pocket because it's out of warranty.
The great dicotomy is that GM owns Allison (for now), and they use the Allison 1000 in our trucks, but GM spec's a different fluid (Allison TES-389 DEX VI) for the GM trucks, while Allison recommends the TES 295 TranSynd. To me it's kind of a "good, better, best" mentality. The TranSynd (and equivilants) are the premium choice. Unfortunately, during warranty, you're not going to be covered for running them; with the '06 and later models, we must run DEX VI licensed products to stay within warranty. My warranty drops off early, but yours goes on for quite some time, meaning you'll pretty much bound to use DEX VI for a long time if you want the GM warranty coverage.
Amsoil and others provide warranty coverage if the lube is at fault for a failure. Unfortunately, we (the consumers) get to sit by, possibly for weeks, while GM and Amsoil or Schaeffers argue about who's product is a fault, and who's going to repair the trans, and who's willing to pay. If you don't think this kind of coporate politics happens, I can direct you to a couple of guys right now that are embattled with GM over warranty claims issues. Not that it's just GM; I had a Ford Mustang in 1989 that was wicked fast when it ran, but it didn't run right 1/2 the time. After trying arbitration, and the State Atty General, I finally gave in and traded it for a different car. I lost quite a bit of $$$equity, but even more the sanity lost from the fight just eventually overwhelmed me; I was without my car for weeks, but I still had to pay the loan note while it sat waiting on people to decide my fate! Anyway, I'm rambling.
MY ADVICE IS STICK WITH WARRANTY SPEC'D PRODUCTS DURING A WARRANTY PERIOD. BECAUSE GM SOLD YOU THE TRUCK WITH A WARRANTY, YOU'RE BOUND TO USE THE SPECIFIED FLUIDS/PARTS DURING THAT PERIOD IF YOU EXPECT WARRANTY COVERAGE.
