I have used them and they work fine, it's in my 1911 now.
I bought the variable because the gun shop didn't have any regular springs at the time.
Typical of the 1911, I've read very convincing discussions on the merits of both in a non-compensated single stack 45. Some gunsmiths recommend them and others do not.
I do believe it allows the slide to retract a bit easier when doing a check. I don't notice any difference when shooting, but I shoot only 'standard' loadings or less- nothing hot!