In the lab where I worked for my previous project the people used only the
Stragenes Quick-Change kit and I also used it to make dozens of different
mutations in a few different proteins. With them and with me it worked 98-
95 percent of the time, respectively.
If you want to check for the possibility of secondary structure formation
in your primers, you can use the netprimer applet or download a free oligo-
analysis program from oligotech (you can find both of these if you just
type netprimer or oligotech in to google)