A Google user
I teach with Hansen & Quinn at the university level and I have found the eBook to be indispensable. My commute is about 30 minutes on public transportation and the eBook has allowed me to keep the hard copy at the office, which is great as the text is large and around 5 lbs. At $18, this is a great convenience.
The major issues are with the TOC/Indexing, pagination and OCR. The major divisions of the textbook, i.e Units 1 - 20, which comprise roughly the first 600 pages are listed under a single chapter named "Front Cover". In addition, the pagination of the eBook is different than the hard copy although luckily the scans often include the original numbering. Lastly, the OCR is unpredictable in book English and Greek and sometimes confuses the two, e.g. the contents of p. 829 are listed as "ENOEiδH-OHEEK Vocabulary". Because the OCR is so spotty searching the text is unpredictable and not particularly useful (esp. in Greek).
The convenience of the portable/web-accessible version of the book outweighs the formatting issues. Hopefully, an updated and reformatted version of the textbook will be available soon.