I don't feel like using caps really often but I need text-transform:uppercase more often without letter-spacing.
As mentioned in #147 :

Another option is to remove letter spacing from caps and have new classes for letter spacing, which feels more basscss-like - @skattyadz

I think it would be easier to maintain and work with new classes for letter-spacing (of course, with new variables!)

.ls2 { letter-spacing: 0.1125em }
.ls1 { letter-spacing: 0.075em }
.ls-in { letter-spacing: initial }
.lsn1 { letter-spacing: -0.01em }
.lsn2 { letter-spacing: -0.025em }