It is a feature, but not the one you mention. That would still allow focusing, even if you do not half-press first. The idea is that by fully pressing the button quickly you can skip the autofocus, to make a picture more quickly. It is also present on the N82 (and N95?), but there you have to press really quickly to skip the focus (which works better imo). Ajjara, try Live Focus to add a manual focus option. That makes the N900 a better macro camera than the N82, in my tests in any case.