Nota bene: I am a Mac user, and this review is only about the products interaction with Mac OS 10.5.
The IRIScan express 2 beats the DSmobile 600 hands down in terms of Mac compatibility, but that was still not enough to encourage me to keep the product. Despite the great OCR functionality of Readiris Pro 11 and the promise of convenience of Cardiris (which I did not get a chance to use), the software interface and workflow has a "we just managed to get this out the door" feeling to it. The interface is not at all Mac-like, and the scanner does not, on the Mac, provide a TWAIN or Image Capture driver. That lack forces you to use the provided clunky applications to make any scan.
Despite Readiris's outstanding OCR performance, the PDF output is less than optimal. The Windows software included with the DSmobile 600 (the only portable, sheet-fed competitor that claims Mac functionality [and doesn't deliver]) produces perfect facsimiles of scanned pages and adds OCR text to the PDF that allows you to search and index it without losing the character of the original document, just like Amazon's "Search Inside This Book" feature for those of you who haven't experienced PDFs like this. Readiris Pro does not have this feature. Its PDFs are what you would get if you took the text document output and printed to PDF: disappointing and not at all useful for archival purposes, my motivation for purchase.
Also, the scanner is EXTREMELY slow, and all-caps are deserved in this case. The scanner takes more than 60 seconds per page. This is impossible to use if you are looking at a stack of documents you need to digitally archive. Enough said. If you are looking to do paperless office on the Mac platform, you need to use either a sheet-fed all-in-one machine from Canon or HP or, even better, get the Fuji ScanSnap, which at $600+ is insanely priced but works like a charm... so I've heard.