I suppose the overplayed and over-sweetened renditions of the Four Seasons are to blame for the general view of Vivaldi as being cheerful etc.
Let me change your views a little bit:
http://www.youtube.com/watch?v=SVh78k2ZzYk
I suppose this late piece is neither cheerful nor does it sound like the Four Seasons, does it?![]()
I also notice his late works are becoming darker and more dynamic. Also, I think the key to discovering Vivaldi as much underrated are good performances. Most of them will give you this cheerful, oversweetened feel. However, consider Giuseppe Carmignola:
http://www.youtube.com/watch?v=6IMT1j-rE2E
Apart from Carmignola giving you the proper violin, I hugely admire Trevor Pinnock for his harpsichord as well as conducting (yes, he does this rare combination). Perhaps you would like to take a listen on his rendition of "La Notte" - again one of the darker pieces:
http://www.youtube.com/watch?v=A29r8oZ6qC4
Since I made the discoveries mentioned above, I noticed that Vivaldi is unique in a way. He turned out to be a very keen observer of sound - not only music, but also the everyday sounds - flies flying by bottlenecks etc. as well as birds, frogs and other things. I have the impression that his music is the power of nature rising at his command - which has nothing to do with the oversweetened look forced on his reception by the mass culture...