While searching for a potential upgrade to my Rebel XTI (400D) camera, I came across a message thread about a new firmware hack for Rebel XTI.
I've given it a try and after the hack, it seems to work as advertised. It now has ISO3200 and some more ISO settings in between the default ISO settings, like ISO500. The most interesting thing to me is the added spot metering mode. At one time, I was considering if I should upgrade to a Rebel XSI for the extra metering mode. One other added feature is checking the actual shutter count.
For the curious/adventurous ones, the following is the thread:
Firmware hack Rebel XTi /400D enables ISO 3200, Spot metering
* Disclaimer: if you/your friend decides to try it, do it at your own risks. I will not take any responsibility for damage/negative results.