I have a Galaxy Ace (bought today) and I hate how the keys pop up as you type, iPhone style. On my Nexus S (stolen) you could change it, but I can't seem to find it on this.
I don't know if you can change that but you can always install the same Keyboard that you had in Nexus S. Search market for Gingerbread keyboard and/or Ice cream sandwich keyboard.
Those keyboard are the keyboard that ships with Android. Samsung like HTC modifies/creates keyboard that differs from stock keyboard. Samsung keyboard is very much similar to ios. But unlike iPhone style, you can always change keyboard in Android OS.