Each of Wagner's Ring cycle operas offers conductor and performers a continual stream of opportunities for "wow" moments. There are moments of humour, bars of intense power in the music, crises in the drama or passages of intense vocal lyricism - there are so many possibilities that it's impossible for any one performance to capture them all. One way of evaluating a Ring cycle opera is to consider how many of these fleeting instances were seized upon by orchestra and cast with enough impact to make a lasting impression in your memory.

Measured by that yardstick, Fabio Luisi's conducting of Siegfried at the Met last night was intermittent. When the flashes of brilliance came, they were very bright indeed: top in my mind is the prelude to Act III, just before Wotan summons the earth spirit Erda from her sleep in the abyss, where insistent string figures surround huge, deep chords from the brass: exactly the sort of high adrenalin musical thrill that keeps you coming back to Wagner. A less obvious but equally potent moment came in the dialogue between Wotan ("the Wanderer") and Alberich in which Wotan tells Alberich that a hero will arrive and win the Ring. The scene is accompanied by a powerful statement of the "Wälsung" motif that is attached to Siegfried: the shock induced in Alberich was palpable. But while the orchestral playing was technically excellent throughout - lustrous brass sounds, clear woodwind voices, perfectly synchronised string playing - I found it all a little too clinical: the number of occasions where the orchestra really lifted me out of my seat was smaller than I would have wished.

Several of the vocal performances, however, did give me that lift, most notably that dialogue between Wotan and Alberich: Marc Delavan and Eric Owens magnificently captured their antagonism. Owens's voice dripped with hatred of the god who has robbed him of his power, Delavan's Wotan (who, at this stage of the narrative, is more or less beyond caring about his impending doom) was urbane, sardonic and sneering. Another duet that came through superbly was the conversation between Fafner, sung by Hans-Peter König, and Jay Hunter Morris's Siegfried. In Robert Lepage's staging, the dying Fafner turns back from a dragon into his original giant form - permitting König to use his normal voice as opposed to the distorted dragon version (for which, bizarrely, Wagner's stage directions mandate the use of a megaphone). In König and Morris's portrayal, both the crude giant and the callow hero acquire a measure of nobility in the most improbable of circumstances, as Fafner tells his story to Siegfried in words that the ignorant teenager cannot possibly understand, but whose weightiness mark the start of his process of maturing.

Morris was an engaging and likeable Siegfried. His portrayal was less loutish than many, with more emphasis on youthful high sprits and less on teenage angst and casual brutality. I was initially worried about Morris's vocal power, as early passages in the low part of his register vanished under the weight of the Met orchestra, but those concerns were allayed soon enough. Morris definitely showed the required combination of youthfulness, bell-like clarity and immense stamina that is such a particular requirement of the role, and I enjoyed listening to him more and more as the evening wore on. As Brünnhilde, Katarina Dalayman was every bit as good as in Friday’s Walküre. Her voice is pure and smooth with little resort to vibrato, forced into a screech only on a few rare high notes. The dynamic control is impressive: I often heard her carefully altering the weight of voice during a single note to lend some particular character. Most importantly, Dalayman is a natural actress, looking as credible in intimate moments (such as the "where am I, what's happening" of the sleeping beauty re-awakened) as she is in the grand sweeping gestures of the subsequent love duet. Not a great deal is going to make me view the last scene of Siegfried as one of the greatest Wagner ever wrote - I find the text drags for too long and the emotions unconvincing - but Dalayman and Morris did about as good a job of it as I can imagine.

The cast's acting was generally good, although for my personal taste, Gerhard Siegel's Mime was somewhat overacted, with too much emphasis on trying to get humour from a parlando (semi-spoken) singing style. The use of Robert Lepage's complicated moving set was more muted than in the earlier operas in the cycle, and I don't think it worked as well. In some cases, it was overused: the video-projected forest would have been perfectly effective without being continually put in motion, with the attendant clunks and creaks, during some of the most sensitive pianissimo music in the opera. In others, it was perhaps underused: Wotan's summoning of Erda, so effective musically, was distinctly tame on stage, not helped by an unfortunate costume for Erda which was stitched with dozens of mirrors to reflect spotlights into the audience's eyes. Other areas looked a bit cheap: the dragon was large but reminiscent of a child's toy; while it was a perfectly good idea to use a video projected woodbird which leaps into Siegfried's lap, the quality of filming of the woodbird (and, briefly, of Wotan's ravens) simply wasn't good enough. To sum up the staging, I'm going to borrow a phrase from Douglas Adams: it was mostly harmless.

All things considered, this Siegfried was a mixed affair. There was much to enjoy and much to marvel at; there were times, especially in Act II, where the performance felt as if it might achieve real lift-off, but it never quite achieved the sustained momentum of Friday's Walküre. The Twilight of the Gods awaits - a very different sort of opera. I'm hugely looking forward to it, with no real idea of what sort of performance to expect!