I use a pressure cooker regularly. If you follow the instructions, they are quite safe. Make sure you don't exceed the recommmended volume, especially for foods that may foam (could block the vent pipe from releasing excess pressure).
Pressure cookers can significantly reduce cooking times, especially for foods that are cooked for long periods of time. I cook stews in my pressure cooker and get wonderful blending of flavors and tender meat. (Just be sure to add the more tender vegetables such as peas AFTER the pressure cooking step or they will cook into mush.) I also cook artichokes in the pressure cooker.
Presto is a good brand. I wouldn't go with a cheap one. Pressure cookers have the potential to be dangerous if poorly constructed. Even though the good quality ones are quite safe, I wouldn't to be working around a cheap high pressure vessel!
Stew recipe (all ratios are to personal taste so no measures are given): In bottom of open pressure cooker at med-high heat, heat cooking oil and brown cubes of meat. Add chopped onions at end of meat browning so they cook in what is left of the oil a little bit. Add water and chunks of potatos, carrots, other vegetables that you like in your stew (except tender vegetables which will be added later). Total volume should be no more than 3/4 of the pot size, and water should cover all the ingredients. Close pressure cooker lid according to directions, turn heat to high, wait until steam has been escaping from vent pipe for about a minute to make sure all the air inside the pressure cooker has evacuated and only steam is inside, then put pressure regulator on vent pipe. Start timing when pressure regulator is rocking steadily, cook for 20 minutes, cool until air vent falls indicating that pressure inside is low enough to safely remove lid. Remove lid, add tender vegetables and enough water/flour mix to thicken the stew. Add Kitchen Bouquet to taste.