Just tried the beta, and it definitely is fast.
I have around 5000 books in my library 360 of which are on the Kobo. I simply marked all 5000 of them in the library view and started the "Store" process as a background job.
Calibre needs nearly a minute to preprocess stuff (I assume it creates a list of all books or something) and the "Store" process needs 3 seconds.
Yay :-)
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