I've done it before on and off, and am going back on it today (after getting slightly bored with WW) but I thought I'd track what I'm eating on WW to see how many points I'd be using whilst doing SW, IYSWIM.
I haven't quite added it up but I know if I'd been doing WW today I'd have gone way over my 21 points.
And yet it works! How, dammit?!