I listened to All-Consuming Fire, Guy Adams' adaptation of Andy Lane's Sherlock Holmes crossover New Adventures novel, with Nick Briggs as Holmes.
I don't remember the book that well -- I read it when it came out, and not since -- and several of the scenes that I do remember (the third and seventh Doctors in the Diogenes Club, the meeting with Mycroft) weren't present. I thought the audio play worked though; its first half is, basically, a Sherlock Holmes story guest-starring the Doctor, and the second half reverses that.
I wasn't really that taken with Briggs' Holmes. I'd only heard his Holmes performance once before -- a Christmas freebie in which Holmes investigates Santa Claus -- which didn't leave much of an impression. I found him to be overly mannered, like Matt Frewer on quaaludes.
All in all, I enjoyed it. As a mystery it's not much, but it's generally fun.
And Watson, you sly dog, you!