I definitely agree with what everyone has said. The difference between clips/clipless is huge. You may even notice that you're working different muscles (aka they'll be sore) in the beginning.
I agree with Fujigirl about unclipping as you approach somewhere you're most likely going to have to stop. I unclip and rest my foot on top of the pedal and coast up to stops. That way I don't slow down too much and then have to try to clip out before I tip over. It's getting down the quick stop/clip out that takes a bit of time. You'll get it eventually. It'll become like a reflex for you. Just keep practicing.
"Only the meek get pinched, the bold survive"