I was a long time 18-55 user before I got the 16-55. It's very rare I actually miss the OIS, in most cases OIS is valuable when the shutter speed dropped below the 1/FL - and if I'm shooting anything that moves (people, streets, vehicles, foliage) I need 1/100s at minimum to have any chance at stopping blur - in those cases OIS was of no benefit, but the extra stop of light at 55mm on the 16-55 was. In the end the biggest difference of moving to the 16-55 has been the complete edge-to-edge sharpness improvement wide open vs the 18-55, I have no hesitation using the 16-55 wide open at any time, whereas on the 18-55 I tried to stop down to f/5.6 whenever there was enough light.
If having the OIS is of primary importance, just keep the 18-55 in your stable and then you'll always have the option. After a few months my 18-55 was just never getting used.