This is a tougher choice than I thought it would be. I'm thinking of starting a poll!

On the one hand, the Super Jolly seems like a reasonable upgrade to the M4 (unless you head over to the coffeesnobs forum...). On the other hand, the idea of even fluffier grinds, much faster grinding and perhaps somewhat less day-to-day tinkering with grind settings is very appealing to me. The added size and issues with the interlock collar on the new Majors are annoying, though.
I don't really see myself buying a conical or anything really crazy beyond this any time in the next few years, so I don't want to let that idea influence my decision. I'd certainly like to make it a big upgrade I won't regret and end up upgrading again later. Hmm... To update prices, we are talking about C$885 for the SJ or C$1300-1400 (depending on whether I can call in a favour with a visiting friend) for the Major.
Whatever grinder I buy, I definitely want to run it off an external timer. It's not so much for dosing (I weigh all my doses) as being able to thwack and distribute in the PF basket without having to worry about turning off the grinder in the middle so I don't overshoot. This is probably a topic for a separate thread, but I'd certainly be interested to see what you're putting together, Cecil. The only feasible options short of tinkering yourself seem to be the 1s Waring timer and used (ugly!) darkroom timers on eBay.