I think you have selected the right one,you may pay a little more by purchasing S5,you may not like its
big size,average low light performance,slightly above average dynamic range,annoying red fringings at
full zoom.
But consider the unique things that S5IS offers:-
F/3.5 at full telephoto
Powerful Flash
12x optical zoom with 128 zoom steps(Available also during movie)
Continuous AF in Movie Mode
Exposure Control in Movie Mode
Stereo Sound Recording with 44kHz sampling rate
Wind Filter
Ultrasonic Zoom Motor
Best Movie Quality of All Canon P&S
Actually if you want a 'current' canon P&S cam to shoot high quality movies,then S5IS is the
best choice. (Some people prefer it even to the hybrid TX-1 that claims to deliver "HD" video)
If you are not lured by megapixels,you may be interested in buying an S3IS which will be
less pricey and offers nearly all the features above except the extra megapixels and unusable
high ISO. If you are not interested in long zoom & movie mode,then plenty of alternatives are there.