All the way through my CD journey I have switched between plans - SS during the week, then SS+ at weekends, then moving between SS+ and 810.
It has worked for me as it fits in more with my life style, and it hasn't affected my losses as far as I'm concerned.
I am now on 810 and am consistantly losing 2lbs a week. Not a huge amount, but I'm virtually at BMI25 so know my losses will slow.
If you can stick to the diet, and not feel deprived mon-fri on SS, then I have found it a great way to 'play' the diet.