It seems that way to me. A shirt that would take anywhere
from 30 seconds to 2 minutes per frame to calculate in Poser 5
now seems to take only 5 to 7 seconds. Same shirt, same character,
same pose. I can really blast through getting clothes to fit now.
And it seems a lot more stable haven't noticed any lock-ups yet.
Is it just my set-up, or has Curious Lab significantly
improved the Cloth room engine?

The technology is licensed from Size8. They might have made some improvements.

I finally gave P6's Cloth Room a try. You weren't kidding about the performance improvements ...,

I was using the reverse-shrink-wrap technique to make a tight-fitting tube top for Furrette, and P6 ripped through that sim in seconds.

That's a new one on me, The reverse-Shrink-Wrap technique, im interested in how you do that one?

I think thats where you size down your model place a loose fitting prop over it, scale it back up to 100% around frame 15 or so and run a cloth sim on it. Poser will dynamically conform the prop for you. There is a pretty good tutorial on the web if you look (I think I found it searching period dynamic clothing poser in google, but I could be wrong)

Yea here it is LD this is the method of which you speak is it not?

Yes, more or less. In this case, though, I'm only using the cloth room to mold the fabric around the figure's body. After it fits, I'll take it back into my modeling application to add more detail, then turn it into a conformer.

As far as performance goes in the image above, I should also point out that I was using a relatively low-resolution mesh (~600 polys) at the time. As I continue making the item, I'll subdivide it to increase its polycount.