(Night After Night got there first, so a few quick words mostly agreeing with that account.)
Handel operas can be something of a trial: all those repeat-laden solo arias leave little behind which a poor singer can hide, and little distraction for an audience subjected to one. Of course, they also give plenty of space and occasion for a great singer to seduce with tone, and display her full range of vocal color. The most "authentic" thing in Handel performance is star quality.
Hercules isn't an opera, of course, being from his later English-language period. Nevertheless, as the hero's jealous wife Dejanira mezzo Joyce DiDonato comes close to this ideal, showing power, finesse, and a straightforward ease in seeming unhinged. Being still just in cutesy pant parts at the Met, it's a pleasant shock to see just how deep and broad her talent is. DiDonato makes the show -- see her. (Incidentally, despite general convention she gets the last solo bow.)
The rest of the cast is never less than pleasant, often more. It's always good to see William Shimell in something substantial, and the lean, pure, but not insubstantial soprano of Ingela Bohlin is another happy discovery. William Christie conducts with unceasing life and energy, and his orchestra leader Patrick Cohen phrases his third-act solos well.
BAM's electronic acoustical "enhancement" system, of which I've previously complained, seemed either off or on good (that is to say: minimally noticable) behavior. There's no reason for there to be empty seats at this, especially for the first nights of a four-performances-in-five-and-a-half-days (insanity!) run.
And no countertenors (well, except for the chorus)? Go.