The Blackbird is a very nice cartridge for what it is, a relatively inexpensive, high output MC cartridge. Is it the best cartridge that I've owned? No way. I have owned cartridges like ZYX UNIverse, Dynavector XV-1s, Koetsu Rosewood Signature, Lyra Helikon, Transfiguration Phoenix, etc.
Due to the economy, I have downsized significantly. My current system cost is roughly 20% of my previous system. However, I am always pretty amazed at how close the sound comes to the more expensive rig. Maybe all of the "huge improvements" I was noticing over the years weren't so "huge" after all.
Anyway, high output cartridges are supposed to sound noticeably slower, I can't say this about the Blackbird. It is quick and agile. Airy and extended through the highs, the bass is tight and tuneful. The bass is not as powerful or punchy as some of the Dynavectors I've owned, or the ZYX 4-D, but then you can't have it all in this price range. In my new system configuartion I was somewhat limited do to using a VAC preamp with a built in MM phono stage. So low output MC's and their high price tags were not a consideration.
So for what it is, a modestly priced, high output MC, it is very good indeed. I have a feeling the reason that it has lost popularity is two-fold. First of all, it has been in circulation for almost a decade now, with no Mk II or Mk II revisions. Audiophiles like their revisions, just look around. Secondly, the price went from $750 to $1099 about two years ago. That is almost a 50% price increase. I'm not saying that it is not worth it, it is still highly competitive at the $1100 price range sonically, but it will take the market a little while to adjust to the 50% increase in price.....especially without a Mk II or Signature tag to apply to it.
That is the way the market works. FWIW, I saw one listed on Audiogon a week or so ago and it sold in one day at $600.