Machine Vision Advice

If you are a custom machine builder, sometimes you might include machine vision as part of the overall control scheme. I'm sure you have considered the pros and cons of just buying a turn-key, all-in-one vision sensor package vs. something more versatile and powerful, even if it means you will have to do some of the component integration yourself to have the in-house expertise. The software for these machines can be the scary part of the whole process. Can anyone give advice about both approaches?