we all agre : the electric collar should be used only for extreme measures and when all other methods are failed.
We tried an E.C. on our arms : a light bite, far lower than a phisoterapic machine...but the result of bad use can be devastating for the relationship between man and dog. Using it on a sennsible dog like a CSW, more sensible than many other dog, is not the right way.(IMHO)
for regular training , simply, it is useless...you can achieve the same good results (maybe in more time) without it.
at our training field there are dogs (not CSW, we are only two) that win competition or take good places, without any use of E.C....
...by the way, these dogs seems VERY HAPPY to train ! (seems that at our training fiedl, we are all in the "second group" : more rewarding than penalisating)