so many people said image stabilisation is not needed for the 17-55mm range. but i will say, if possible go for the lens with IS/VR/VC/OS, whatever you call it.
IS will open up new grounds for you, especially when shooting still subjects with lower shutter speed and high ISO. being able to drop a stop of ISO(e.g 3200 v.s 6400), will mean a huge load of noise and details saved.
50mm @ f2.8,
ISO 1600, 1/10s
vs
50mm @ f2.8,
ISO 8000, 1/50s
IS also allows you to 'drag' the shutter speed while maintaining some form of handhold-ability to create mood shots like this:
Olympus OM-D E-M5, 20mm @ f2.5, ISO 200, 1/10s, shot from waist level.
i am always in favour of capitalising on technology to create better photos. so yes, if your budget allows for a Canon 17-55 IS USM, then please go for it. else the Sigma 17-50 OS HSM will do fine too.
PS: shutter speed, not
shuttle speed.