i love how everyone ignored my above post... :)
If you plan on shooting primarily in low-light situations but still want to buy a non-HD single chip camera (for the cheaper price, I guess), then the canon cameras are probably going to be the best choice (in that ilk). The optura (and I'm pretty sure they put the feature in th XI too) series has various exposure settings built in to the quick select on the camera. They also have menu accessible "manual" adjustments for Iris/Exposure etc..
However, the low light settings are only nice to low action. I was able to shoot some decent looking late night outdoor shots with the optura, but it required a tripod and some patience. The preset setting worked all right, but it was a bit better, after setting it manually.
Keep in mind, the outcome wasn't HD quality or anything, but it documented the time shot with later viewability.
If you're wanting a small camera to take spelunking or something, then the XI will do, but you'll want to invest in some high-output led flashlights.