CardScan for Mac software had excellent OCR accuracy in my testing and is quite capable as a contact manager. In addition to managing contact data, the software also allows you to drag-and-drop the ubiquitous .vcf files that Outlook attaches to email signatures into CardScan in one step. It also features an image view and can map contact information via Google Maps. One improvement I'd like to see is the ability to drag-and-drop a block of text to CardScan and support for Apple's data detectors.
A brilliant new feature is CardScan's automatic synchronization to Address Book which is a boon for Mac users as it keeps your iPhone up-to-date and synchronizes with the rest of the Address Book ecosystem. If you need to get data out of CardScan you can export contacts in vCard format or to Address Book.
I previously used an IRIS Business Card Reader II (IBCR II) and found it to be serviceable, but much slower in the scanning department. If you collect or own a lot of business cards the CardScan Executive is a great way to clear off your desk.