I just got my BLF Special Edition D80 yesterday! My initial impressions are good.
One concern I have for the OP is that the D80 does not have any circuits to help guard against over-discharge. That is significant, because attempting to recharge a Li-ion battery that has been severely over-discharged can be dangerous, especially if the battery has been stored in that state.
I own neither the Convoy S2 nor the Convoy M1, but I believe they both flash the main beam on and off when a battery gets too low. If you see that, you know it's time to change the battery. Afterwards, you should recharge the old one as soon as possible. Li-ion batteries can degrade when stored in a fully discharged condition.
Other flashlights, such as the BLF Special Edition A6, have a low-voltage cutoff that turns off the flashlight completely when its battery gets too low. This is an effective way to guard against over-discharge. First, the A6 steps down to lower levels, for instance, from High to Medium, and then from Medium to Low. You get some runtime at these lower levels. The final step-down, from Moonlight mode, turns off power completely.
The D80 is in a strange middle-ground. It uses a high-amperage driver. To get the best performance, therefore, you want to use a high-draw IMR or INR battery such as the Samsung 30Q. Typically, those batteries are unprotected. On the other hand, the complete absence of any system to warn you when a battery is too low argues for using a protected battery such as the protected KeepPower 3500mAh or the protected Evva 3500mAh. A protected battery has a circuit that turns off the battery when voltage is either too high or too low, and also when discharge current is too high.
Of course, the main line of defense is the flashlight user. The D80 will dim to the point of being useless as battery power wanes. When the operator sees that, it is his job to change the battery before it gets too low.
The bottom line is this: if the OP will learn proper care for his Li-ion batteries, he can minimize the risk of having any problems with them.
At present, I have a 30Q battery in my D80. I am confident that I have done my homework on both the flashlight and battery. I am comfortable, therefore, running "naked" (i.e., without any protection circuits). Nevertheless, I am planning to try a protected Sanyo/Panasonic NCR18560GA at some point, probably the Evva brand that is selling for $9.95 USD in the USA at Mountain Electronics. If performance of the D80 is "sufficient" using the GA, I will probably stay with it.