Yes and no. Simply moving a app to the trash will indeed delete the app, but now all of it's associated files. This could include app specific documents, preference files, and more, which over time can take up space that could better used elsewhere.
It really depends on the user and just how many apps they install though.
To fully remove apps, I use TrashMe on the app store. http://www.jibapps.com/en/products/trashme/