I'm raising CX for the first time. I had 14 for a bit (just processes 6 as Cornish game hens), and the smell is a non-issue. Well, while in the brooder, there was a smell problem --despite being on fermented feed from day 1, they eat a ton, and therefor poop a ton and that doesn't work too well in a small brooder in a small house. Now the broilers are in a 6x5 A-frame pen, and are let out 2x a day for a couple of hours. My 6 laying hens have their own coop, but all the chickens are let out into the yard together. The layers ignore the broilers for the most part--the lowest hen in the flock tends to chase the broilers around, but that's fine, gives them needed exercise!
I'm in the southwest, where vegetation and grass is NOT plentiful, and their pen is on dirt. I'm in the midst of doing deep litter with the broilers--at 6 weeks I'm putting in fresh pine shavings every few days. When they are all processed, I'll rake it out, have some fabulous compost, and the pen area will be...back to regular ol' dirt. Mine seem to be growing more slowly than I've read about, but they are on restricted food (more of a work schedule thing than a feeding regime) and were outside without heat from 1.5 weeks old. Oh, 6 of them are the slow-growing broilers, so that's to be expected, though they still seem small. The 2 regular CX are 6 weeks, and not near to being ready to butcher as a full-sized chicken.