My favourite thing about SAGA is the ease of use - all the tools are intuitive to pick up and use (and you can learn it very quickly, too!). The tools are very powerful and can tackle almost every geospatial problem - from simple raster analysis and data manipulation to complex spatial analysis and GIS development. I have used SAGA in a range of applications, from simple image processing to more complex GIS analysis. The SAGA team are very responsive and always willing to help - and it is free! There are a few bugs in SAGA that need to be fixed - eg. the raster data management is a little cumbersome. It is a very powerful tool for any geospatial problem - and the support is fantastic! I have used SAGA for a variety of applications, mostly in the agriculture and fisheries.