He's dreadfully English - anyone bored by Tallis' simplicity would have nightmares with Sheppard, but it's likable despite how homogenious his output can sound. I didn't care for his masses, but this disc was a good find:

Comments are often made about English early music ensembles draining the festivity out of continental European choral music, but the incredible precision of a group like the Tallis Scholars really underlines what is already implied in the spare and unambitious style of Sheppard.
You can't go wrong with a Stile Antico disc, all of their HM issues have had stunning reviews.