http://www.datadirect.com/products/odbc/informix
Using the same feature set as its industry standard ODBC drivers for major relational databases, Progress DataDirect offers a Platinum ODBC driver that:
DataDirect's Informix ODBC driver delivers the same advanced feature set of our industry-standard ODBC drivers, offering robust functionality, better performance, and higher availability than any other Informix connectivity solution.
Progress DataDirect (http://www.datadirect.com/)