Originally Posted by geoffwood
My 3GS is running IOS 5 quite happily. As to Siri, I suspect it runs as well as "Google Now" runs on ICS, which would be not at all, at least not in any supported way.
Google Now doesn't run on ICS because it has dependencies satisfied only on Jelly Bean, not because some company tells you the hardware suddenly is not powerful enough to run it (especially when the app was actually running on that same hardware, Siri anyone?).
Note that Google Now can be hacked to work on ICS, but it will not have the same voice prediction capabilities as on JB (hence why by default it requires JB). It's a genuine reason, unlike that given by other companies.