Mozart's Don Giovanni is an opera that is most difficult to classify. On the one hand, it has many of the trappings of a traditional opera buffa: a fast-paced farce with people falling in and out of bed, master and servant switching clothes, a buffoon-like manservant sung in the bass register and so on. But Mozart was rarely a conventional composer: he throws in some high drama, some moments of heart-lifting (if not entirely sincere) romance and some philosophical musing on the nature of evil. The music and mood switch constantly between hilarity and utter seriousness.

It's a high-risk opera to perform. When everything works, the listener is dragged along with the emotional roller-coaster and comes out light-hearted, a little chastened and humming the tunes. But if the music, singing and acting don't come together, the evening can feel long and disjointed. ENO's new production had several good things about it, but I didn't feel it came together well enough.

My biggest concern was the orchestra, conducted by Kirill Karabits, who has a fine career on the concert podium but relatively little experience of opera. Don Giovanni opens with a huge D minor chord that should hit you like a truck, followed by a massive build-up of tension, preparing you for the fact that very bad things are about to happen. I simply didn't feel the desired impact. Throughout the evening, the orchestral playing was clear and accurate, but I kept feeling that the whole thing was a bit leaden - a thought that was confirmed by the production ending a full 25 minutes later than its advertised time.

There was much good quality singing: clean, lovely and precise. Plaudits must go to Sarah Redgwick, standing in at very short notice for the indisposed Rebecca Evans as Donna Elvira and providing the most vivacious, engaged performance of the evening. Robert Murray's Don Ottavio was appropriately wimpish and yet tugged brilliantly at the heart-strings in Il mio tesoro. But a great deal of the singing seemed strangely divorced from the action: Iain Paterson has a lovely baritone voice, but didn't come across to me at all as the evil, sneering rake that is Giovanni. Brindley Sherratt's Leporello was fun but fell short on the rapid-fire low-register passages that are opera buffa's trademark. Very close to the end of the opera, Matthew Best was the first of the singers to pack real high-intensity punch as the Commendatore summons Giovanni to repent or be damned.

The translation, by Jeremy Sans, strayed beyond recognition from the original text, to the point where it would have been better labelled as "a new adaptation by" than "English translation by". By the end of the evening, I was thoroughly fed up with it. The original Don Giovanni carries a full payload of sexual imagery, and I don't think it helps to add cheap puns about "someone's coming" or to translate "sotto a una fenestra, fare all'amor" as "shagging in an alley". Despite myself, though, I enjoyed the biggest piece of hatchetry: the famous "catalogue aria", in which Leporello details the list of Giovanni's conquests to Elvira, was completely rewritten and performed as the accompaniment to a PowerPoint presentation complete with charts of conquests by month. It brought the house down.

Rufus Norris's production was one of those which don't think there's enough material in the opera and which feel the need to add a load of additional visual material of their own. There was much shifting of scenery, much running around the stage by servants in spooky demonic clothing, we spent the overture on a flash-back of Don Giovanni's previous rapes, and there was an episode whose point I didn't get at all in which Don Ottavio strips down to his underwear and is dressed again a short while later by Donna Anna. The setting and costumers focused on Don Giovanni's sordid nature, culminating in Leporello serving the final dinner on paper plates with bread coming out of supermarket carrier bags.

I left the Coliseum rather disappointed: for me, the pretty music and singing didn't really make up for the drab staging and the lack of dramatic impact. I'm not sure the rest of the audience agreed - there was rapturous applause for the singers in the curtain call.