I've been using one in my 71 for probably 10 years or so. I like the ratchet action much more than the mega shifter I had before. It is a lot easier to move the shifter between gears. You can ratchet up and down with it, so if you are in second you can go directly back to first or up the back down etc. If I remember right the mega shifter worked the same way just not as smooth.
I got the one with a shorter stick, I think it was 2in shorter,I dont think they offer it in the shorter version anymore.
I know Hurst makes one that is very similiar but when you pull the handle up and shift to drive it actually stops at neutral and you have to ratchet to drive. then to go back to park or reverse you have to ratchet back to neutral and then pull up to get out of the ratchet gate to shift back up. If that make any sense. Kind of a pain after using the Quick Silver.
Also I beleive you can modify the Quick Silver by removing a rivet to make it a full ratchet from park to low. The mod used to be in their instructions.