While I never got that flat-top 066, I do have a pretty nice running round-top 066. It's not stock of course, and is a really strong saw. Although my recent addition of the 500i has supplanted it somewhat as my main falling saw, nothing will ever totally replace my 066...I really love that saw lol.
I used to not see the big deal with them, but I've become an 044/440 fan in recent years. I've got more time messing around with 044 porting than everything else combined, so I have a pretty good idea what makes them tick. One of my freebies I ended up doing a ported 046 hybrid on, that became my main falling saw for awhile. I hit all the marks on that one and I'm really happy with how it turned out. My other 044 is disassembled right now, I was experimenting with some rather radical port timing numbers on it(cheap aftermarket cylinder,) and I went too far on it. Between playing around with both saws, I've learned a lot about port timing, compression, and how they relate to each other.