I have had one ( a Kuhn Rikon) for many years and I love it! There are some things that just not are the same without one. If you have Madhur Jaffrey's 'Quick and Easy Indian Cooking' you can get a lot of inspiration in how to convert the long cooking times of many Indian recipes to a pressure environment. Indian cooking with it's long braises is one of the best uses for a pressure cooker- other quick cook traditions will not have the recipe opportunities available.
Another great author on pressure cooking is Lorna Sass- she has a few books out helping with the concepts and safety of pressure cooking. Many of her recipes are meat based because that is one of the best uses for a pressure cooker- breaking down the connective tissue and fats in cheaper meats that usually require long cooking times. I would never make any kind of meat stew in anything but a pressure cooker. (20 minutes vs 3 hours and more tender results!)

Read the instructions, follow the safety advice, and never leave the kitchen while it is on. One needs to know their stove very well and keep a really close eye on the cooker. They are safe, especially the new ones, but you do not want to pop your safety valve. You can let the extra pressure out if it is building up too fast, but after some use you will know the combination of pressure you want to maintain and the setting on your stove that will do it.
Follow the recommended capacity for the food you are cooking- things like rice and beans which froth might plug the valves with the foam produced so you must keep the volume lower than you would in a regular pan. Even foods that do not produce a lot of foam must not over load the cooker. They are actually not meant to be filled much more than half way, so buy a big one if you are yet to invest in one.

A note on beans- they will turn out firmer than the long cooking technique. I made basic New Orleans type red beans and they never did fall apart into the creamy gravy consistency that is the goal there, but that is not always what one is looking for. Just keep it in mind and have fun experimenting!

Something to consider is a pressure canner- if you have not purchase a pressure cooker yet...they are larger to accommodate canning jars but I do not know if they are acceptable to be used for cooking food in them. If they are and you wanted to cook beans, that seems like a way to have increased volume that might be worth investigating. I have been studying up on canning and pressure 'cookers' are not appropriate for canning (low acid foods) because of the smaller volume.
Anyone wish to address this aspect of the conversation?