Just another bit of input on SRAM vs Shimano shifters. My BF builds custom bikes for a living and works regularly with SRAM, Shimano and Campy parts. In his opinion, SRAM is a more elegant and mechanically simpler set up, making it mush less prone to failure. The engineering in the different levels of SRAM groupos is the same, what varies are the materials and the weight.

As for the different shifting, most Shimano shifters have essentially 2 levers to shift, the long front lever that is also the brake lever and a shorter lever behind it. To shift one direction you push the big lever in (both levers actually move when you do that), to shift the other direction you push in only the short lever behind the brake lever.

SRAM uses one shifting lever behind the brake lever. So you're not messing with your brake lever when you're shifting. To shift one direction, it's a short push in, to shift the other way it's a long push in.

I've used Shimano, SRAM and Campy shifters and I have to say that I prefer Campy, but that's way out of most peoples price range. Between Shimano and SRAM, I definitely prefer SRAM.

Hope that helps.