The first half is rather slow, but keep going - it's definitely worth it. The humour in Hitchcock's films is generally based around great character actors (e.g. Jessie Royce Landis in To Catch a Thief and North by NorthWest), and here not one of the actors disappoints. Lillian Hall Davis has a better part in the Ring (also 1928 - Gordon Harker is again very amusing in it too), but is lovely in this film. Sound would have added nothing. My 8-year old daughter was apprehensive about watching a silent film, but once things started to get going in the second half, was hooked.
Hitchcock referred to it in later years as one of his "photographed plays", but the action occurs in several locations, so is nowhere near as constrained as many of his films (plays or not). In fact, even though the location shots are few and far between, they really give this film a non-studio feel.
All of Hitchcock's films are notable for their visual storytelling (look at the initial scene-setting in Rear Window that speaks volumes without a single word being uttered), and it is interesting to see the origins of this, and the great influence of German Expressionism.