I’m not actually monitoring HD – we shoot in HD, then down convert and capture/work in SD via firewire – or we shoot in DigiBeta and capture SDI.
To monitor my signal, I am going SDI out of the DeckLink HD Extreme into my DigiBeta deck, then going component out of the DigiBeta deck into a Samsung LCD widescreen. Full screen, real time, very slight lag (less than 1 sec.) no issues.