I don't have the range extender yet. I am still considering adding it. My bike is primarily used as a commuter, so it remains to be seen if I want/need it. Having come from a regular Vado to the SL, I've already noticed, by my rough estimate, about 30-40% greater range for the SL on identical routes, but using consistently less assist.
And yes, I replaced the seat post with a Kinekt 2.1suspension post. I also replaced the saddle with a Selle Anatomica H2. I love both. The folding lock is an ABUS Centium model (which was their special edition version last year, I believe) It's a bit fancier than the standard black ones and it comes in a big wooden box that's great for storing souvenirs, such as those picked up on Humboldt County rides.
I got the folding lock at about a $40 discount by ordering through BikeInn and shipping it from England. It took almost three weeks to get it, though, as they use USPS.