Haven?t seen much written about Dropper seat posts. I have a RadRunner plus. The RR+ is a great ride but a bit unwieldy when coming up to a stop sign or when trying to punch a pedestrian crossing button. It most offen requires getting off your seat to plant your feet the ground.
A suspension seat post is a good upgrade but I find that a dropper post is a much more effective upgrade than a suspension seat post in urban riding conditions. If you don?t know what a dropper post is, it is a seat post that has a button on your handlebars that you push to drop the seat to lowest possible seat height. Push the button again And the seat returns to your optimum riding height. For me it is the number one mandatory upgrade. Another useful technique is to drop your seat when going down hills. Lowers the center of gravity and improves down hill riding safety. They cost about $200.00 up. Here?s the company I got mine from - http://pnwcomponents.com/
Call them and they?ll set you up. Have a tape measure handy, so you get the correct length. Love mine. I have no Relationship to PNW other than being satisfied customer.
A company based out of Seattle has a suspension dropper post combination you might want to check out. They have a good reputation although I don't currently have one.