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We have had a few over the years. The latest can be set to run for a number of hours then it drops to warm so the cooked food doesn't get cold. We make a lot of pulled pork or roasts in ours. It takes a while to cook anything but it usually turns out very good and moist.

I bought a very simple compact one as I have a tiny kitchen. It has a simple knob with three settings - low, high and keep warm - but there are wonderful ones with delayed start, timed cooking etc. I have found it very useful, especially when it has been hot in the summer and you don't want to put the oven on.