OCR is a bit of a resource hog.
The review doesn't say how instantly or reliably it decodes a section of text.
OCR is really the sort of thing that either ought to be integrated with iOS/Android down low where it can be optimised, or handed off to some meaty engine somewhere in The Cloud. Google presumably has access to decent OCR IP from all the pirati^H^H^H document digitising work it's been doing recently. I don't know what Apple's OCR history is.