The Geospatial Technology journal Directions Magazine has just published a Q&A with IBM's Director of Data Servers Bernie Spang: Informix Spatial Data Technology: Update and Positioning. The article discusses the Web Feature Service Datablade module, the Spatial and Geodetic blades. Also mentioned is the R-Tree index design contrast between Oracle's and Informix's spatial offerings.
My favourite recent example of Informix datablade solutions (including spatial) at work is the Impire AG live action sports content.
Informix Spatial Data Q&A