Greg Sandow has an interesting piece up on Handel's operas. His comments on Handel are factually accurate, though he seems to have missed the fact that Andrew Huth, writing in the Guardian, is making many of the same points he makes. I think Greg leaves out a few things, though.
For one thing, we're living in a golden age of Handel performance. It's worth remembering that his operas were probably not performed between the 1760s and the revival of Rodelinda in 1932. These days, it's unusual not to have a couple of Handel performances during the season in a major city. Locally, we've got Flavio running at Pocket Opera and Belshazzar's Feast at Philharmonia Baroque. Ariodante is coming to San Francisco Opera in the 2007-8 season. I wish I were in London, where I could see seven in four months.
Now, about that 1932 Rodelinda revival. Kirsten Flagstad sang in it. No, I can't believe it either, but it must have been something to hear: astonishing nobility of tone and no idea of the style. While Greg is right that most ornamentation you hear in Handel today is more discreet than you would have heard in the 1740s, it's important to keep in mind why that's the case. For one thing, singers today are being trained in a variety of styles. They're expected to be able to sing vocally-appropriate roles from three centuries. Thus, they're not spending all their time learning how to sing like an 18th c. virtuoso. It takes time to reconstruct a historical style!
We're still living in an age when there are multiple pools of singers with the skills for Handel. Members of the Pocket Opera cast probably won't be singing at the Met, but they can sing Handel. Very likely ten years from now there will be more and better vocal improvisation, too. While there's not an opera fan alive who wouldn't pay folding money to hear Farinelli in full cry, we can't go back to committing human rights violations to ensure a steady supply of a particular voice type.
Lastly, there's the matter of the goings-on in the opera house during Handel performances. I, for one, would love to have an adventurous opera company recreate that atmosphere; I'd travel to be in the audience. But I think it would be a little like the Society for Creative Anchronism: the 18th century as we would have liked it to be, not as it really was. We don't want all of 18th century London, anyway: dust, wood fires, open flames for lighting, sewage on the streets, rotting food, horse manure all over the place, smallpox. And much as I'd like to sometimes experience the opera house as it was in the 18th century, sometimes I'd like to sit quietly and just listen. Handel's operas are great even without visual spectacle and Farinelli-esque vocal fireworks.