I have got the kind that has a freezer built in. If you want icecream, you switch it on and pour in the mix, 30 minutes later, you are tucking into icecream. Its a wonderful luxury. As with any premium icecream, if you have stored it on the freezer, it will need to soften before you serve it. Pro's are that its delicious, that you know what's going into the ice cream/sorbet/frozen yoghurt, that you can make flavours that you can't buy. Cons are that the machine is expensive, that you can't just get it out when you need it as the freezer part has liquid in it that needs to settle after you move it (like a fridge)
I have got this one
Amazon.co.uk User Recommendation
if you go for one, I would recommend that you get one where the paddle motor churns from underneath. In the Magimix Gelato Chef model, the motor is attached to the lid and the lid fastens to the body with very weak plastic lugs, the strain from the motor broke the lugs off after a year and it wasn't repairable. Some models also have no separate inner bowl, the bowl is fixed inside the machine which makes cleanup very difficult.