Discussing firmware upgrade in Canon PowerShot S3/S5 IS. CascadeHush says: Though my S3 is enjoying a relaxed (though not completely passive) retirement these days, It did get a lot of use... at no point has is ever crashed, locked up, or displayed any abberant behaviour.
Neither is it missing any obvious features. So as far as I can tell, there is no need for an update. I did try a hacked firmware once, that allowed me to shoot RAW and had some other features, but I didn't really think it was worth the bother. Discussing shooting RAW in Canon PowerShot S3/S5 IS. Downloads. CHDK currently has two official branches: The branch labelled 1.2.0 which is considered to be 'stable'.
This branch is used for minor changes and bugfixes, backward compatibility between updates and has more stable code and behavior. The branch labelled 1.3.0, also called the "unstable" or development trunk. This branch contains minor and major updates, some updates which might be not backward compatible. Using it involves a little bit of risk. CHDK Download - build 0.9.9.