Most office files are created with Microsoft Office and quality of conversion is defined by the degree to which it is the similar to what this suite creates - at least for visual appearance. What limitations do alternative converters have for Word, Excel or PowerPoint documents? What about emails created or received with Outlook? What about information beyond appearance: e.g. text encoding for search, tagging or metadata? Are there differences in quality of PDF code in general? Which solutions provide the best stability for automated conversions?
A vendor neutral presentation with as many answers as I can give.