I've used it before and it hasn't failed me even once.
Many people yell me it isn't really good.
Not that I use a Blaziken but I just want to know.
Double Kick: 30 BP Physical Move.(Fighting Type)
Each "Kick" would give you an approximated Base Power of 45 thus achieving a total of around 90.
One kick may or may not break a Substitute. Whereas Hi Jump Kick, the preferred Fighting type move has a base power of 130 which gives you an approximate base power of 195. That is why Double Kick is not used much on Blaziken.
The approximated base powers are not exact and the final damage might be more or less.