I did a Brisket on my Weber Perfromer a couple of weeks ago, I was considering picking up a SNS, but then I just decided to go with the same method I have used for year smoking Thanksgiving turkey. Bank coals to one side using Firebricks/ minion method, water pan under the food. I Grab a beer or in the case of a brisket a 6 pack ( a brisket is a bout' a 6 beer 2 whiskey smoke).
I think the SNS is an awesome device, I also like the hack where people affix 2 weber coal baskets together to make one large basket.
I just don't think the cost or the hassle of storing another accessory is worth it since my slow and low method isn't broken.
I did buy a Vortex and will try that for my next indirect slow n low cook.