Yes, there's a few extra steps you need to take to get it to work properly! You need to create "projectname/media" in your umbraco site and put the special web.config file that you'd normally put in the media folder in there too.

Finally, assuming you're on V8, you need to register the virtual path provider in a composer to wire it all in. This is the composer code:

    [RuntimeLevel(MinLevel = RuntimeLevel.Run)]
    public class MediaFilePathFixComposer : IUserComposer
    {
        public void Compose(Composition composition)
        {
            composition.Components().Append<MediaFilePathFixComponent>();
        }
    }

    public class MediaFilePathFixComponent : IComponent
    {
        private readonly SupportingFileSystems supportingFileSystems;
        private readonly BucketFileSystemConfig config;

        public MediaFilePathFixComponent(SupportingFileSystems supportingFileSystems, BucketFileSystemConfig config)
        {
            this.supportingFileSystems = supportingFileSystems;
            this.config = config;
        }

        public void Initialize()
        {
            //IMPORTANT: The virtual path is hard coded to /media in the S3 provider, so we MUST override it here in order to get the correct image paths displaying on the site where we are using production bucket paths
            var fs = supportingFileSystems.For<IMediaFileSystem>() as BucketFileSystem;

            if (!config.DisableVirtualPathProvider && fs != null && config.BucketPrefix != "media")
            {
                FileSystemVirtualPathProvider.ConfigureMedia(config.BucketPrefix);
            }
        }

        public void Terminate()
        {

        }
    }

This will check if the bucket path is anything other than the default media one and register the virtual path provider.

I've raised an issue on the Umbraco.Storage.S3 repo, but it's not been fixed yet as far as I can see.

Hope that helps!