For reader’s convenience, the bottom of each page indicates the portion of the biblical text covered in that page’s facsimile, with hand-written notes over the facsimiles to indicate the starts of chapters.
The quality of the scan seems to be quite good. Below is an excerpt from Deut 30:2 (on pg. 248) showing the asterisks and metobelus used to mark what seems to be a revision toward the text represented in the MT.
There are features in the interface for commenting on the variant unit and a link that will take you to the local stemma and coherence modules for said variant unit. There is also an option to see the unedited collation data, a list of patristic citations (fuller than in the print edition as I understand it), the Vetus Latina collations, and a nice feature which tells you how many conjectures have been offered for the variant unit and a link that will take you to the data in the Amsterdam Database of New Testament Conjectural Emendation.