Just a few impressions of the integral out of the package. I think its just thin enough for most rocky mountain summer backpacking. My size M was 7.5 oz, the same weight as my beloved (size L) I/O bio contact hoody. Just from holding it up to the light it looks a little more densely woven. I'm betting more durable, but a little warmer/less breathable. My I/O is a little warm for hot summer days, and the dark gray makes it hotter under the sun, so I was looking for a lighter colored and thinner hoody that would work well even on those hotter days.
Out of the package, I'd definitely recommend this as a backpacking piece, but it didn't offer any real advantage over my I/O, so I'm returning it. The other thing, which I think makes I/O wool better than any other I've tried, is that the weave is sort of loose and open, and it uses %4 elastin. I immediately noticed with the slightly tight MH integral that it was restricting my motion a little bit, and it didn't have that nice stretchy quality to it. Not sure what I/O has done with the contact hoody, or whats even going on with them as a company, but so far thats still the best I've tried.
Before getting injured this winter, I was also succeeding at spending a good number of days sheathed in my black I/O bio ninja suit, which I would hole heartedly recommended as both a winter base layer and go to stealth ninja attire.