It's just odd... that for a project that seems to be dedicated to "unlocking the disabled features of the hardware"
That's not an accurate description of CHDK. CHDK gives you
- More information: e.g. histogram, zebra, OSDs
- Additional control and flexibility: Force particular settings, scripting, remote control.
Sometimes the control includes going beyond Canons specs, but I wouldn't say that's the main point of CHDK.
there is little mention as to what the hardware is actually capable of :S
The figuring out the exact behavior of the different overrides requires measurement for each specific camera. Most people don't do this, probably because they don't have much need for the extreme overrides in the first place.
Going from experience with models that have been carefully measured, you can expect the following:
- Shutter speed overrides work far beyond the Canon specs, in both directions.
- If the camera has an adjustable aperture, you can usually go a bit smaller (higher F stop) than the Canon specs, but the value is limited.
- ISO cannot be overriden significantly (or indeed, at all) beyond the limits of the Canon firmware.
For an overview of CHDK features, I suggest
http://chdk.wikia.com/wiki/CHDK_User_Manual. Most features are available on most ports, hardware permitting.