anyone use the pacsafe mesh product to protect their backpack on extended travel? What did you think?

Yes.

It's very fiddly to use - my pack isn't huge so the 'cord' has to be pulled quite a bit to make it fits snugly around my bag, which means there's then lots of cord to do something with before I can padlock it in place...I find myself having to weave a lot of extra length in and out of the mesh. Note that it tends to get caught on straps and pockets as I'm trying to get it into place....don't think you can put one on in a hurry!

It's also a pain having to keep taking the shoulder straps of my pack apart if I want to have it protected AND be able to carry my pack.

And expect to struggle to get it back into it's little bag!

I only do shortish trips now and only use it for countries that are notorious for theft / bag-slashing, although I guess if I ever had anything stolen, I would use it all the time again. For peace of mind, it's worth it.