My 4 running OS5 does have this feature in Settings, so while I've not tried it myself, I'm guessing the answer is 'Yes'.
I've no burning urge to move up to the 4S - the features and speed on it not enough of a carrot to encourage this incremental move and all the stuff I need to do works fine as-is - but if you're coming from an older iPhone or other device, my inclination would be to go with the 4S, if you can afford it. You'll end up with the newest technology and be set for the length of any contract you may get. The reported 'battery drain' issue seems to be an OS5 - not hardware - issue and Apple has (finally) acknowledged it and tell us a fix is in the works. Apparently.
All that said, if push comes to shove, I think that storage, rather than processor speed, is a bigger issue for users, particularly if your plans include loading up the device with music, video and games. If you can get a iP4 with, say, 32 GB storage for significantly less less than a 1P4S with 16GB, I'd go with the iP4.
I think I've sufficiently muddied the waters for you. My job is done here...