Should be no problem with either MCU - nothing in the firmware special for either. I bought a few V's in the beginning and freely mix them up. Just fyi, I did some low voltage testing on a 85 (no V). We run them at 10 Mhz btw. I could run the light down to 2.3V without a hitch, accept the LED was a very light glow. I was pretty much amazed btw. The 350 mA 7135's, maybe combined with DEL's new 25/85 circuitry allows us to run with a PWM value of 1 with no prob, even on a drained cell. The 85 is spec's down to 2.7V, but add 0.2V for the diode, and you have 2.9V as spec'd low, but it ran on a cell at 2.3V, and since the LED is totally useless at that level, I don't see any problem at all. I literally had to cup my hands over the head to see the LED light up, and could only tell it was lit from turning ON/OFF - slight difference. I don't recall ever being able to do that, or anyone else posting bout it!!
Dunno, dunno why - maybe the 85 PWM rates, maybe DEL's great tweak on the circuit, maybe the 7135's, but the 7135's is the same batch I bought from FastTech years ago, maybe a combo of all these things.
I've been buying all my 85's from Richard - dirt cheap, cheapest around, and all he has is the 85's no V. Since basically no one has been buying them except for me, he's still got 55 in stock at that great price. I'm afraid if they ever do get popular, he'll have to buy a new batch and charge twice the price. His price is $1.35, while Mouser is over $2 in qty 10 or so, last I checked. Richard literally makes pennies on these things - amazing he even bothers, but he's there to help, not just sell/make money.
Ohhhh - btw, the spec sheet on the "V" says 1.8V-5.5V only for clock rates of 0-4 Mhz, which Narsil doesn't do, or bistro. For 10 Mhz, it's spec'd exactly the same as the non V MCU's: 2.7V-5.5V
Oh bout the clock rate, it is, and must be 10 Mhz -- the fuse values are for 10 Mhz, and the code/build is for 10 Mhz. If you want to tinker to lower the rate, by all means go ahead. I think DEL, maybe couple others used a lower rate fine, but PWM rates I believe will go down quite a bit. For me, I see no point in dropping from 10 Mhz, but the option is there. We had discussions bout MCU rates a while back in the 25/45/85 thread. Think Halo wanted us to go lower as well -- forgot, another reason as well, maybe...