Based on my experience, here's what you need to know to make your own Custom Fit sweater a big success (pun intended):
Remember that this is bottom-up knitting. No top-down knitting is provided in Custom Fit. Amy Herzog, the creator of Custom Fit, is a big proponent of seams because they improve fit (and she's right, IMHO). She does provide guidelines for making the garment with a minimum of seams, however.
Take accurate measurements. No denial, my friends. The measurements need to be based in reality. Don't guess either. Get someone you feel comfortable with help you get ALL the measurements required. No fudging, either. If you want the sweater to fit, you must enter the correct measurements.
Make a gauge swatch. Yes, you must swatch. Just get over it. You have to make a 4-inch x 4-inch swatch and then you need to wash it and measure it again. Custom Fit makes your pattern based on a specific stitch and row count. Again, no fudging!
Add ease below the waist. Custom Fit is designed to create sweaters the skim the body. This works great if you don't have a mighty derriere like I do. If you're even remotely plus-sized, I think you're going to need more ease than the pattern gives you. Check out the Custom Fit projects on Ravelry and see if you agree. Many of them are too snug through the hips for my taste.
The good news is that Custom Fit lets you "pop the hood" and make manual adjustments to the pattern before you purchase it. Select this option and manually change the hips measurements (or whatever you need to change). To determine how wide your sweater should be, measure your favorite knit garment - sweater, T-shirt, anything that has some stretch. Enter this measurement in the "pop the hood" section. You will be happy you did.
Check the length, too. There have been some complaints that the sweaters are too short. This is another measurement you should check on your favorite garment. You can adjust this in the "pop the hood" section.
That's all my advice for the day. I'm looking forward to making a lot more Custom Fit patterns - I've got a million ideas rolling around in my head, and Custom Fit makes it a lot easier to make these dreams come true. I look forward to hearing about your experiences using Custom Fit.