I swapped the stock can out for a carbon Remus about 10 months ago. At the time, I was trying anything to make the high idle, bucking bronco thing go away (this is before I/we understood it was the airbox and not air/fuel).
Anyhow, the weight savings was pretty big - I think it was about 8 lbs lighter! Which of course on a bike is a good amount. That said, I noticed no improvement in MPG or handling. Sounded nice though!
I also swapped out the filter for the fancy pants billet piece and oiled filter at the same time.
I had a nasty backfire POP! on decel that I could not get rid of - no exhaust leaks anywhere and only happened when letting revs fall down past 3K. I just learned to live with it but had plenty of friends jump when they were "shot at".
In the end, I swapped back to stock a month ago before taking my bike in for the airbox service...I didn't want any BS about the mods causing anything so I just eliminated that from happening altogether. When I went back to stock, I have to admit I liked it...enough to leave it. It's quieter (which on the GT is good for me- the Duc can be as loud as she wants but touring quietly is nice).
What's more - my MPG went up going back to stock..from a several month average of 42.1 mpg to 43.5 after just a week or so.
So I have a Remus can gathering dust in the spare closet along with the little intake. Some folks love the swap, and I thought I did...until I went back to stock.