"Half" shifting -- what and why?

[VeloVT]

This is actually a really nice feature. My new bike (ultegra) has it but my older bike (older ultegra) didn't -- and I find it really helpful. I have a bad habit of riding in 39-12, and if I couldn't trim the derailleur I really couldn't use that combination on the new bike without serious chain rub. I actually have to trim around 39-14 I think.

(I know somebody's gonna tell me I shouldn't be riding in that combination anyway ).

Are your shifters/fd 105 or Ultegra? I find it's quite easy to do a full shift all at once on my bike (2007 Ultegra, I think). I have another bike with older 105 that requires a serious, hard shove to shift into the big ring that I think would be difficult for those with small hands (it's pre-"double shifting", no trim available), but I've heard newer 105 is better in that regard.