I love using my IP as a slow cooker and I don't have any trouble with it.
The trick is to bring it up to temperature using the Saute function first. This has the added benefit of being truly one pot cooking. Use the Saute function to brown/sear the meat then sweat the veggies. Add the meat back to the pot along with your other ingredients. Then set the slow cook function.
Just to be sure, because of all the naysayers, I used a digital thermometer to test my chili one day. Using my method, it was 202°F after 4 hours.