No, as alluded by Jstar, there are linear polarizers and circular polarizers. Some sensors, like the sensors on Canon EOS digital SLRs require a circular polarizer otherwise the metering/focusing (I can't remember which one) mechanism will give inaccurate results. Beyond the linear and circular dichotomy, there's also a special manufacturing process that results in some the higherst quality polarizers, the Kasemann* process of laminating the polarizing film onto the glass surface. If you've got deep pockets, Kasemann is the way to go.
* My apologies to the punctilious germanophones for omitting the umlaut over the first "a" in Kasemann and yesterday in Gelandewagen in another thread.