There are two things to consider about this: the restoration and the new soundtrack.
The restoration is utterly impeccable as far as I can judge. There is not a speck or scratch on the entire presentation, and the tints for each of the scenes render beautifully. There is still the warmth of age with faintly inconsistent colours to the tints, but I think any clearer and it would start to lose its authenticity. It literally is the case that you can pick out the individual stray hairs on Ivor Novello's head. Particular highlights for me include the 'flashback', where the Lodger reveals his story to Daisy (which is a beautifully contrasted scene, lighting-wise), and the love scene where they lingeringly kiss: it is a beautifully shot and glowing piece of romantic imagery, occasionally equalled but rarely surpassed in the rest of Hitchcock's output.
The score I think will divide people. I was present at the premiere of this restoration, where Nitin Sawhney conducted his band and the London Symphony Orchestra, and it came across really well. On the DVD in your front room though, I'm only 90% convinced.
The score itself is excellent, delicately orchestrated. Daisy's theme is brilliant: slightly kooky, with some brilliant syncopated rhythms as the strings rise through the basic ditsy theme. The first thing to get your head around is that Sawhney has seen fit to reference Bernard Herrmann quite prominently throughout the score, so we have clear nods (or even wildly deep bows) to North By Northwest and Psycho, and a hint of Vertigo too. I must admit, my heart sank when I heard the two or three 'Psycho Murder Scene' strings, which punctuated little points in the film. But I think it took almost a conscious effort to 'be okay' with this, actually the score holds together really well I think.
The other thing to get your head around is the use of vocals in two points of the narrative. When Daisy and the Lodger are growing close, Sawhney deftly treats the sequences like pop videos, and has written songs with words to express what the characters are feeling. In concept it works reasonably well, but I've got to say I think a lot of Hitchcock fans are going to reject this.
The question is: do you take someone else's authored work and author your own on top of it? Or, more simply, should silent films have speaking (or sinigng) in them? Sawhney in his question and answer session was quite relaxed about having done this, but the overall effect is I think to draw you away from the Lodger and challenge you with a whole new artform: the 'voiced' silent movie. I'd argue that at these points the soundtrack ceases to 'support' the movie, and instead becomes part of it, changing it. Sawhney mentioned in his Q&A about how nice it was not to have a director to placate, and I think this is one of the areas he may have been overruled.
And yet, Herrmann was allowed the rule of the roost at times, so who knows? Be prepared, though, Hitchcock purists. This was the thing that, live, I thought worked ok, but on the DVD jars somewhat.
But, get it for the restoration, for the love of Hitch!