Whenever considering a P&S for low light, work out what the physical pixel size is. Signal to noise is directly proportional to pixel area assuming everything else is equal.. The pixelsize of the sensor in this camera is 1.9 micron square. The 350D is 6.4 micron and the ratio of area is about ten to one. The 350D will have ten times the signal to noise of the Canon Ixus 900 Ti.
Large pixel numbers are just marketing hype in P&S. Their noise at ISO 100 is about the noise of a 350D at an ISO of 1000+.
Look here for sensor sizes etc.
http://www.dpreview.com/reviews/specs/Canon/
They are designed for one thing taking pictures at high light levels and even then the noise is quite noticeable if anything higher than an ISO of 100 is used.
Bert