Mostly but not entirely true as SRAM Attack series shifters are Shimano compatible. SRAM also makes Shimano compatible derailers.
SRAM shifters with names (Attack, Rocket, etc.) are Shimano-compatible, the numbered ones (X11, X5, etc.) are not.
I dislike twist shifters too, I like these Shimano trigger shifters, myself:
http://www.ebay.com/itm/Shimano-Altu...item33a2453cea. They come complete with cables and are easy to install.
Microshift also make Shimano-compatible shifters:
microSHIFT -The best control system
Use the Park instructions to set them up:
Park Tool Co. » ParkTool Blog » Front Derailleur Adjustments Park Tool Co. » ParkTool Blog » Rear Derailler Adjustments (derailleur)