That being said, I would certainly look at other options at 5k. Maybe you find better maybe not, but look all the same. I know for 5k you can slide into some really really nice used mills.
I won't speak for anyone but myself but in my case I don't WANT a one-ton piece of iron in my garage unless I never have to move it again, and given my history, that ain't gonna happen until I retire. Oh, and that phrase of "there are plenty of GOOD used mills out there doesn't apply around here. Sorry. The only ones I've seen locally in that price range are completely worn out POS like that one my friend bought. Back East is probably different, but many of us don't live there.
When I bought Blue (PM25) that was the biggest machine I wanted to deal with while I'm still working. Same for the SB 8k. Then along comes this 12Z thingie. Very similar work envelope to that PM935 Taiwan machine that I have had in the back of my mind for when I retire, but without 'most' of the weight. And cost. As someone stated in a different thread, the CO 12Z is probably pretty close to the rigidity of a BP clone given they carry the majority their weight in the base and knee. The head of a BP/clone is on a sliding/rotating knuckle for flexibility of usage. I've seen some of those commercial 5-6 thousand pound 'real' mills. Now those give new meaning to the term rigid. The flip side is they are completely unusable for a guy like me. In my life everything seems to be a compromise... *sigh*
Anyway, I was having some problems with Blue (my fault, I bought a pulley kit that I 'assumed' was properly designed. It wasn't. Now I have to fix it.) and started thinking that there has to be SOMETHING out there that can give me most of the capability of a Boat Anchor (i.e., big arsed knee mill) that I can move without having to have friends with large hulking moving equipment. I talked to Ray C about a 932, but in my envisioned use case I would have to upgrade the motor and install a VFD to get the speed range I want. Matt has 'em, but I'd be putting it on myself and probably voiding my warranty. Probably not a deal killer by itself, but...then there's my biggest personal itch with those machines: the lack of travel in Y. Most of the RF45 variants can't even cover their tables in Y. Then it gets even worse if you install a DRO scale on the back of the table! This is not something I am willing to deal with. Do I need 12-13 inches of travel in Y? Not at the moment, but who knows what I'm doing years from now? Fairly certain I don't.
So then I get wind of this big hulking (for a hobbyist bench style bed mill) thingie from Charter Oak. After doing some cursory investigation, I find it's a re-hash of a IH(?) mill some of the home CNC types use/used but not without having to upgrade/mod the thing. Great. Another Chinese kit machine. NOT something I'm really into at this point. Then I had a few conversations with the folks at Charter Oak and even a customer of theirs or two. The major flaws of the previous design were addressed. Steps were taken to improve the build process and overall quality. Upgrades are provided for those who would like some of the big-guy features without having to go 'all in' on a boat anchor (oiling system, tool changing system, etc.). But the major selling point for me was that they use the same mill for the basis of their CNC mill. The ways are trued and ground. The machine is already designed for a oiling system. You simply have to drill and tap a few holes to install it (so I'm told. The proof will be when I install that upgrade myself, but NO ONE ELSE offers this as an upgrade). Oh, and the head/column interface was improved/enlarged to increase rigidity and improve longevity: that thing is huge for a mill this size!
Long story short, I decided to get it. After all the talk, it's the only way to know for sure.
(why couldn't I have taken up knitting as a hobby...)
Also add a 8% sales tax on the Grizzly machines for me. Those box ways are sexy though.