It will just hang on the limiter.

 

I use it when merging into highway traffic. I come off the ramp in 3rd and depending on traffic ahead of me and on the highway I will hit the go pedal pretty hard to get up to speed and join the flow.

It's really fun to see the semi's getting really small in the rearview mirror so quickly

 

In genereal its irrelevant, Ive used it on normal driving a couple of times, doesnt change a thing. While towing its more useful but the towing mode in combination with the select shift (which limits the gears available) makes it irrelevant there most of the time too! Manumatics are essentially useless since (of course) there is no clutch! IMO the whole idea of a manual is the clutch so you can feather the power delivery of the gear you're on exactly when you want to. Its far from just how fast it switches gears! Furtheremore, a manumatic doesnt let you swap multiple gears in one motion, you have to tap the darn thing 3 times to go from 6 to 3 rd, well, what if you were in 5th rather than 6th to begin with????? You cant have real manual control with a button and without a clutch, period. At best all it allows you to do is to downshift the tranny for slowing down when driving "enthusiasticly". I forgot one thing it is also useful if you want to start moving in 2 rather than first in slippery stuff, but, you can also do that by putting the tranny on 2 instead of drive.
Basicly..... its a gimmick