When I'm in sport shift mode, I don't accelerate hard. I accelerate just as anemically as if I'd been in the normal shift mode. Small throttle openings at higher revs will put less load on the engine than small throttle openings at low revs (lugging it). If you had (or have) a vacuum gauge in your car, you could visibly see the difference between the two. There's very little "control" of this with the VX and it's automatic however. It's a very small window of benefit from what I can tell.

One other thing I do that I forgot to mention is put the car in neutral at stop lights while waiting. Again, you're loading the engine less.