I waited for a long time for a Caly 3 and I just picked one up here on the Exchange last week. I'd handled a Caly 3 before and I own a Caly 3.5 that I've never used, but I wanted a 3 to carry and use. It seems to me that the Calys are getting really hard to find in "like new" condition, but the ZT0566 can still be purchased at retail. If I were you I'd grab the Caly 3 while you can at that price. If it turns out you don't like it, just stick it away for a while and you might be able to trade it for a BNIB 0566 soon!
I'll never understand why Spyderco disco'd the Caly knives, but I bet they hold their value and gain value as supplies diminish. Even if you never choose to sell it, you basically have a knife that's a Delica+ and who could ever complain about that? (same could be said about the GB1 vs. the new GB2)