I seem to recall that the beneficial effects are only really pronounced if you're quite unfit.
In fit/professional cyclists there was no measurable positive effect.
I posted a link on the last beetroot thread we had that suggested something like that, as I recall. There are a number of other articles on the subject just a web search away.
It's not the beetroot itself that does the trick, it's an enzyme produced in your saliva when you eat beetroot.
I didn't vote in the poll BTW because I have no idea whether there's a benefit or no.... but I do like beetroot!