I've used it in the past, to good effect. I combined it with my no-communicating with the humans period first thing in the mornings, though. Coffee, computer or notebook, and free-writing immediately on getting up and before I was vocal. It utilized what I called "dream energy". Most dreams occur just before waking, and if I could prolong that state, I got more free-wheeling writing done.
If I had to talk to the kids or deal with a PTA thing or get my own ass in the car and to work, it wasn't the same. When my day started too early to set the clock an extra hour early to get up and write, I'd take a nap, get up from that and write. It worked, but not quite as well as early morning.
Morning pages are good in that they get your mind freewheeling with the words and ideas, get you past your self-editor because you're not keeping the first three pages. They build a bit of momentum, and if you can sustain it, even for a little while, you can put it to use for actual writing.