I use accelerade on all of my rides, which start at about 2 hours and go up in length from there. I've noticed a significant difference in my performance on long rides, but it's a personal thing, and I suggest trying different ones to see which ones work for you.
You might also read this:
http://riderx.info/blogs/riderx/arch...ion-drink.aspx
and this:
http://riderx.info/blogs/riderx/arch...ing-salty.aspx