well, under those circumstances, yes it could be helpful

 

i shift mine manually 98% of the time, and it dosent slip or act any different then it did when i got it, (i wish it was a manual except for those times when i am really really sleepy then i love it) and i am also ATRA certified in automatic trans. and working on gettin my ASE for it sometime... when i get unlazy, but from everything i have done/heard/learned says that maunally upshifting actually increases line pressure, (this weekend i will go home and check my tranny pressures and compare if i get time) but i dont know about maunally downshifiting, but it dosent matter to me anyway i that a t5 swap waiting for me when i get home, or ill just built up this 700...

*eric*

 

When I first got my car I tried manually shifting it but because it's electonically controlled it wouldn't shift out of first into second when I pushed the lever until I backed off the throttle a bit.
So manually shifting is kinda pointless unless you want to hold first before going WOT.