I have no problem with the stop and search policy in theory. It is in the application that problems can arise.
Racial profiling, negative stereotyping and acting on personal bias/prejudice would be some examples. These have been problematic issues in the past when stop and search was in use.
The increased use of metal detectors (arches and hand-held) combined with well supervised application of stop and search may reduce the number of weapons on the streets, and that can only be a good thing.
However, it doesn't address the attitudes and anger of those who feel the need to act out violently, and that is something that also needs to be explored.