Most of the Archiv label cantata recordings by Gardiner released in connection with the cantata pilgrimage were not in fact made on the pilgrimage but up to 10 years earlier (e.g., the recording of The Big Two, BWV140 & 147). This is one of the exceptions. In fact, it has the odd distinction of having been recorded twice - this concert (in St. David's Cathedral, Dyfed, Wales) is also on a DVD. If you have a DVD player, this is the better bet, as it also has a fascinating documentary on the pilgrimage.
For those who like audio only, this is, again, a splendid issue, with one big name cantata (BWV199, the grim-sounding "Mein Herze schwimmt im Blut" (yes, it really did say that)), splendidly done by Magdalena Kozená, who I think may be the only big-name singer who performed on the pilgrimage. The other two cantatas also receive good performances.
JEG really has made his mark on the cantatas.