Four full length episodes. These are unrelated to the story of the anime and more of a side show. First episode is funny. Second one is touching. These both are a 9/10. Episode three and four are really boring though and are more like a mystery show with characters we have never seen and Shana playing the detective. These may be sad for some but it is hard to feel for characters you just met. Ultimately these dropped the overall score for me.
Well.. The last two episode of Shakugan no Shana S is actually my favourite episode of the whole series.
because of the back story before the main series is really touchy. At the end when "all in good time" started to play is still make me feel sad for me until this day. After credit where shana standing at the bridge makes me really really excited for the final season to start air.
Despite being a short ova boasting only four episodes Shakugan no Shana S was able to move me and affect me. I may be rambling on because of my personal like of the ova, but I believe that this ova is worth watching even if you have not watched Shakugan no Shana before hand as it doesn't spoil the main plot and is self explainitory (only in the 3rd and 4th eps though). The leading two eps are more like filler eps in a long anime or show that pop up, but make for a sweet watch (if you watched the origanal or not doesn' t matter too much)
The actual main plot in the second half was what moved me which conveyed feelings of sadness and of acceptance. Being short I did not expect to be moved in anyway by this but to my surprise the last two ep were deep and emotional to ome extent.
On that note I recommend people watch it especially if you have watched Shakugan no Shana but for those who haven't it is not compulsory to watch it first.