Let's see what we deduce from select few scenes:
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we get Sasuke saying he now has Itachi's power added to his own.
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we see the vast increase in Sasuke's chakra quantity. Now we know that jutsu strength is decided by power and amount of chakra. EMS Sasuke now has the power of MS Sasuke and MS Itachi [and Indra's], and has the quantity to match Chou Oodama Rasenshuriken (easily Bijuu level).
That already should give a rough idea of how powerful his shunshin could be right now. But let's get into the feats.
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we get Sasuke's farthest shunshin feat. Not much of a time indicator, but it was a very far shunshin compared to what we normally see from him (10-20 meter shunshins don't even compare to half this distance).
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we see Sasuke shunshin over to Sakura. Worth noting is that he reached her before KM Naruto did.
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we see Sasuke intercept Juubito's attack on Naruto, which is especially significant, because the attack started
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.
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we have some Susano'O activation reaction time.
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we have Sasuke matching KM Naruto's speed (and chakra output). Then we have CS Susano'O
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with BSM Avatar (not exactly Sasuke's own speed, but still fair to mention).
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we have Sasuke's reaction time and insight matching BSM Naruto's, and keeping up with Juubito.
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we have Sasuke pressuring Madara (after absorbing Hashirama's Senjutsu chakra).
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Madara comments on Sasuke's eye, and how it improves his movements (adding to what I stated above).
After the power-up, Sasuke has shown both speed and reflexes as well, too.
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, his reflexes were fast enough that he could use his new jutsu to avoid Madara's lightning strike.
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, Sasuke was able to follow Limbo Madara's movements (something even Naruto was having trouble with), and even catch him with the his sword.
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we see Sasuke's reflexes again, when he stops a charging Madara with his jutsu once more.
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Sasuke chases down and bisects Madara, further showing his speed. Once again, Madara also mentioned the Choku Tomoe as well [
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].
Of course, all this makes sense. He now has the power of the Sage atop his own. All that chakra, and as strong as it all is, of course he would be incredibly fast.