I'll say that when I was there, it was pretty crowded--I had to wait for a spot at the conveyor belt, and when I'd filled my basket I had to wait in line for a build space. But there are numbered spots on the floor at the conveyor, and no one hassled me or hurried me along even though I kept grabbing parts, thinking about them, and putting them back.
And once you're at the build counter all you have to choose are the accent pieces; other than that it's just following CM instructions.
Edit: One thing to note is that if you want to buy a personality chip, you will either need to buy it as part of a droid/chip/backpack package or make two separate purchases. They would not let me buy a personality chip at the counter where I payed for the build without buying the full package that included the backpack--the system won't ring it up. Presumably it goes the other way if you just want the backpack and weren't planning on a chip. When choosing a chip, you can visit a display outside the build area and there will be buttons you can press to hear different sample sounds from the personalities available.
Thank you for the tips. I'm glad to hear that they don't rush you. I expect it to be crowded and I'm fine with that....but I don't want to feel like I'm just grabbing things to get it done! Sounds like that is not the case. Did you get the chip/bag/droid combo when you built? Do you recommend the bag? There are 3 of us (me, my son and my daughter). I wasn't thinking of spending the extra $$$ to get us each a bag...but maybe a chip? We always have some sort of backpack with us so I'm hoping that will do even if its not as "droid friendly" as the ones they sell there. Is the area to shop for the chip and other accessories a high pressure area or can we look around? Are the prices for accessories (chips, bags, combo, etc) listed online somewhere for some pre-shopping?