For a few years now, I've been passing this one up. I've done some reading about who makes Kirkland's Speyside single malt...and it seems it is a mass producer that makes other brands:
http://alexandermurray.com/product-page/#/all-products
Anyway...they offer this 18yr for $55, the 21yr for $79, and the 25yr for $99. Costco doesn't always have all of them around, at the moment they're not carrying the 21 or 25. I've passed on this 18 for a very long time and finally decided to give it a go.
Long story short, it's pretty solid. It's bottled at 92 proof (Levit 18 is 86 proof). I sat it side by side with my Glenlivet 18...and while I found the livet to be smoother and more refined, it wasn't by a large amount. I'll say that until they setteled down, the nose of the two was quite similar. After settling, I found the Kirkland to have a bit more sulfur in the nose...not 100% why I was picking up on that.
Anyway, I'd easily place this between the Livet 15 and the 18. Not quite as refined at the livet...but nearly half the price. Long story short, I don't regret buying it. I'll say that for the same $$, a good bottle of bunnahabhain 12, or glenmorangie quinta ruban are better bang for the buck...but if you're looking for a super-close-to-Glenlivet-18 for nearly half the price...look no further.