The Zero S was only .4 second slower 0-60 and about the same amount slower in the 1/4 mile according to the Cycle World article.
I think the real-world difference is shown in this quote from the article:
"The single benefit that the Brammo derives from its multi-speed transmission is a stronger launch and quicker acceleration. Its 0–30-mph time is 1.61 seconds versus the Zero’s 2.31..."
I don't do much (any) 1/4 mile drag races, but I shoot out in front of traffic at stoplights many many times each day on my job in San Francisco. That liter-bike-beating acceleration is both useful and fun, satisfying, as Adan points out, the hooligan in me.
It was great getting to meet Adan in person and to trade bikes for a sunny lunch hour of riding pleasure. My impression pretty much mirrors his: the E1 acceleration in Sport is a bit anemic by comparison but still plenty to handle traffic situations when needed. I did find myself missing the more aggressive regen.
I would have been totally satisfied purchasing the E1 for cosmetic reasons: the black plastic vs. carbon fiber didn't bother me in the least. And since the shocks adjust from "harder than a rock" to "as hard as a chunk of wood", I'm not sure the full adjustability of the R version is a big draw for my not-on-track riding.
It was interesting to re-experience the stock seat. It was great to feel that I was sitting "down in" the bike again, but I wouldn't trade the connected feeling and lower COG for my comfort. Once I've gotten used to the 2" higher COG, my bike handles just fine for what I demand of it, which isn't much compared to the racers. And my knees like those 2".
Since I followed Adan on this ride, it was great to actually see my blinking LED auxiliary brake lights in action. They really do stand out and send the message I was hoping to send, having been rear-ended twice on motorcycles.
Lastly, I'd like to report that standing around on Treasure Island with the SF skyline as a backdrop, Empulses shining in the foreground, feeling the warm fall noon sun, gentle bay breezes, and talking bikes is not at all a bad experience.