I just put one on this past weekend. Nice looking chain and easy to install.
I have a few thousand miles on the existing cogset, but it is always kept very clean and well-maintained. Despite that I did have a few occassions of a tooth or two of skipping in certain frequently used gears. I'm going to do a bit more riding this week and will decide then if I need to invest in a new cogset. It is always recommended to change the cogs when a new chain is installed and vice-versa so we'll see. This is my first Wipperman chain so it will be interesting to see how the stainless-steel lasts and shifts.
Wipperman stainless will last at least 3 times longer than a normal chain. It hooks together without tools so I like it like the SRAM chains.
Although the cogs should be changed more often than people think, every time you change the chain maybe overkill unless you don't change the chain.
My experience is with the 10 speed chain, none with 9 speed but construction is the same.