Before the new version of vanilla I was playing MW quite a bit on and off, but I'm not sure if I missed anything in the last few updates it's had. But here are my poorly organized, likely rambling, hopefully understandable thoughts.
I too am amazed that more people don't know about Masterwork - IMHO it's one of the best mods for any game ever. It's balanced, coherent, has a ton of content, modular, and quite bug-free. What more could you want? =D
It's not that balanced, pretty damn incoherent, I'll give you those two, and the fact that my stuff is used in it tells me that that last one is an outright lie.
This made me chuckle, so I thought it had to be quoted. I think I lean towards Putnam's view on it a little, although I think it's a great mod that does a lot of cool things; some great, some good, some a little iffy but usually optional. And has quite a bit of flexibility when it comes to choosing what features you want to use and which you don't.
The standardized materials are nice, and definitely helped me keep my sanity when I was newer to DF. But now that I've been playing 40.xx I somewhat wish there was a compromise between standardizing everything and having some of the more specialty creatures keep their materials (Semi/Mega Beasts, Trolls, maybe the sentient races, etc). That way things are a bit more manageable, but you don't lose all of the flavor of Troll fur clothing, or Hydra leather armor.
The number of ways to adjust the mod to how you want to play (for the most part) is also nice, although I could see having so much content getting a little overwhelming at times. And not everything always seemed to fit together smoothly, as opposed to being it's own little addition to the side that can be added on.
One issue I had with some of the options to turn more/less stone, wood, etc on or off is that not everything would really be set up to work with the mod after it was turned back on. From what I remember it was mostly turning more stone ore types back on, which would enable them, but clash with the mods added metal processing/smelting additions the mod makes. Not so much an issue with what the mod changes or adds, as much as not bringing the optional vanilla features that are off by default into line with the mod, so they will work like everything else if turned back on.
The caste system is nice to have as an option, but the military castes seemed a little powerful. And maybe even a tad redundant when it came to Melee options, with me never really using the Guard or Wrestler caste. Having enemies come half naked probably didn't help make combat all that challenging, although I understand wanting to keep the number of items down.
I didn't use the magic system all that much with the constant combat reports being rather distracting, or the magic abilities tending to cause more harm than good (Not always bad). Nor the religion stuff all that much, but not for any real reason.
Having the difference races as playable is cool though. I had a good bit of fun experimenting with the Gnomes over a few forts, especially having a few get diced by their own machinery or injure themselves while using the speed enhancing rocket boots to haul things a little to fast. And the other races seemed to have their own interesting ideas to play around with.
Overall the mod is a cool compilation of different additions and changes. It just seems to need a little smoothing out. Where it needs this, or how to do that, I have no idea.