Now I can't say I have ever heard of pine needles being used in Western cooking, (let us know if you have or know of any recipes) however I do know that they are used in Korean serves and Asian cooking. Firstly because the flavour they impart cannot be substituted and secondly because they are easily available and can be picked directly from the tree.
All pine needles are edible, however the amount of flavour varies greatly so be sure to either ask advice when buying or taste before harvesting.
Alternatively Pine Needle Extract is easily available both over the internet or from health food shops. In addition to having a distinct aroma and taste the extract boasts a wealth of health benefits.
It is said to work very well as a vinegar, and sit comfortably within a gin or cranberry juice.
Flavour - similar to juniper in ways, deep citrus, fresh, clean