well this was my first time back after an 8 years absence, but I went from 97-99 and they had showers then, so I guess they have always had them.
This was the first time I used them though, before that I was all " Pfffff, you're not supposed to shower at a festival"
But what is true: the better you smell, the smellier everyone else is. On friday it wasn't so bad when I was standing upfront in the pit, but by Sunday it got quite a bit nastier when people started to raise their arms to clap. And I'm quite small, so I'm at armpit height most of the time. Not so nice.