Answers to your questions, Sir....
1. Does the Darwin come with a written warrantee?
A.: The maker Evolv LLC and distributor, Nhaler have both stated in writing on ECF and their respective websites that it has a two year warranty on the unit, and one year on the battery.
2. Does the Darwin have a manual?
A.: A manual on the Darwin is available, and I've seen it. IMHO, it's unnecessary. The Darwin is pretty simple to use.
3. Does the Darwin maintain the "sweet spot" once you set it?
A.: Yes, it sticks on the same wattage level until you move the thumbwheel.
4. What is the actual battery life (between charges) that you are getting?
A.: Truthfully, that's like asking how long a pack of cigarettes will last me; it depends on how much I smoke! With a full charge, it will easily last me for a full day of chain vaping. Though I think LR attys tend to drain it a bit faster. The mini USB port at the bottom also provides a way to use the Darwin as a passthrough when I'm using it for an extended period near a wall plug or computer. It's NOT a magical, wonderful, forever lasting power source which is invisibly replenished by pixies when you're not looking. But it has lasted longer between recharges than any other batty combination in any other mod that I've ever tried. And if you're doing HV vaping using stacked batteries, there is truly no comparison at all, period.
5. Does the documentation that comes with it address battery replacement cost?
A.: The maker and distributor have stated on ECF and their websites about battery replacement costs; I believe it is $25 if it happens outside of the one year warranty period. Keep in mind I got one of the first units, so my written documentation was pretty nil.
6. Does the automatic cut-off function activate often?
A.: I presume you mean when the battery is to be cut off. It has happened to me twice after long days of heavy vaping using LR attys. It shows the dead battery icon, which goes away back to the battery depletion icon once it starts charging.
7. How much does the unit weigh?
A.: Good question. I'll try to remember to weigh it when I get home tonight. It is no heaver than most mods I've tried, like the ggts or metal reos. The shape and size do make it very easy to hold and use. It's not nearly as big or heavy as it looks in its photos.
8. On a scale of 1 to 10, how would you rate this PV against all other PV's you have used?
A.: Conservatively, I'd say at least a 9. Outstanding design, features and construction. And if I were not a LV 3rd gen (self juicing mod) fanatic, I'd probably have to say a 10. If you are a dripper or diehard HV vaper, it is a must have mod.
9. Is there any negative comments you have about the Darwin?
A.: Other than the fact that it's NOT a juicer, not really. When using a 510 atty, the inlet holes sit exposed above the connection to the darwin. If you over juice, the excess will come out the inlet holes rather than clog the atty up. A drip cup could possibly be a nice add on to the darwin, provided it didn't interfere with using adapters or using the mod in general.