while there are some folks that really like the CB stainless steel door and especially the latching mechanism, there are others who buy it and find that it doesn't fit that well, either.
^^^ I'm one. I purchased a CB door for both my 18" and 22". If I were to do it over again I wouldn't spend the money. I find they leak as much as the aluminum door did and Chris is right, it's easy to re-form the aluminum door. But even with the leaks it still holds temps very well. I've never been tempted to install a gasket.
After using my WSM for several years, I can't say I've had the urge to do any additional mods. It's a great smoker as-is.