I've had this pressure cooker for 7 months now and so far I haven't had any issues with it.  I've only used it for artichokes (my husband and I love them!) and large beef chunks for stews.  I like very tender meat like in Chinese restaurants.  I never bothered measuring the accurate pressure (who wants to, anyway?!) but the trick I do to keep the steam vent "whistling" is I let the water reach boiling temp in between medium-high heat.  Once the vent starts hissing, I let it hiss for about 5 more minutes.  Then I gradually reduce the heat to low and the vent would keep on hissing.  I used to boil artichokes in a stockpot for an hour but with this pressure cooker, it's done in 25 minutes.  It probably takes less time than that but I never bothered to experiment further with the time.  At 25 minutes my artichokes are super tender and the "petals" practically fall off when I take them out of the pot.  Hmmm next time I'll try 20 minutes.