It is pretty neat to do. The pilots tell you what to expect and such. I have done it in a UA 757 a few times, and man there is nothing like the get up and go of an eager 757.
FYI. They will line up on the runway, get on the brakes nice and firm, and open up the throttles. As then engines spool up, the plane shakes and then kinda shudders for maybe 5 seconds, before they release the brakes, go to full power, and you race down the runway. The initial climb angle is greater than normal, and then about 1000ft I think it is, the power comes back the plane almost levels off, and you stay like this for a few min until out of the "noise sensitive" area, and then back on the power and up and out you go.
all and all a pretty nice departure from the normal t/o procedures.
They're not handing trophies out today