Jim Murray in his Whisky Bible didn't rate the 15-year-old as highly as the 10-year-old, but I think he must have got a duff bottle: his tasting notes sound nothing like the drink I remember.
And now you've made me go and pull out my Jackson's guide to verify. >8-> Which makes me think that I might have been thinking of the Madeira Matured bottling, which was a single cask bottling. I remember seeing it online for about $250 to $300 a couple years back.
(Sadly, I've determined that Jackson's book is good for knowing what's out there, but not much more, as I don't find his tasting notes comprehensible at all.)
My favourite whisky is probably Ardbeg Serendipity -- an accidentally created vatted malt that I was lucky enough to track down a bottle of before stocks ran out. That one is truly special, and I don't have nearly enough left. 
I am jealous. I heard about that one from the
WhiskyCast podcast and knew that, like most of the limited whiskies, I'd never come anywhere near it. >8-\
The other vatted malt I'd like to try sometime, but probably never will, is the Compass Box Spice Tree. That's the one where they matured it with charred oak staves
inside the barrels, to intensify the wood flavor... Until the Scotch Whisky Association decided it was too nontraditional and forced them to stop making it.
