But it sounds like you CAN get the Viper ROM, you just have to deal with long boot times... Or stick with their version based on 4.4.2.
It's really a moot point, I think, because it takes 15-20 minutes to switch to ART. Had I known how long it would take, I would have stuck with Dalvik. I had 281 apps to update and it went on forever. Stupid me did it with the battery at 2%. Plugged in of course, but I didn't get any charging indication, so I wasn't sure. (It was, in fact, charging.)
But beyond that, with any ROM, you're taking a risk. With some, you're accepting compromises. But that's why we do what we do, isn't it? To learn? To experiment? To have fun? To say, "This is why I didn't buy an iPhone"? I'm a conservative flasher now. I just run CleanROM and update it once a month. That's good for me. Scott does good work, and I don't need anything as flashy as Viper. Scott's not porting 4.4.3, he's sticking with 4.4.2 until 4.4.3 is official (maybe until the boot time bug is fixed, I dunno really).
In any case, I don't think anything's irrelevant about ROM posts where the ROM takes a few extra seconds (minutes?) to boot up. Then again, not my call...
HTC One M8 / Verizon / CleanROM