I used to have a 2012 Shadow Aero. After about a year I did the hole saw mod. It was quick. As my wife put it, "Now it sounds like a motorcycle."
That said, it will never sound as good as aftermarket pipes. It doesn't sound bad, but you won't get confused with anyone on the same bike with V&H or Cobras. Also, being a 750 it just ain't gonna have the rumble that you get from a larger displacement V-Twin. With the fuel injection you never get low enough on the idle to get any sort of loping sound except for a second or less when you rev then drop off the throttle with the bike sitting. I liked the bit more sound of the hole saw mod, but on occasion I sort of missed the stock pipes.
I don't think mine was crazy loud. Maybe it sounds crazy in an odd way behind it. I've ridden behind a Shadow VT1100 with Cobra drag pipes unbaffled (which is what I ride now). It was a bit loud. His had an odd ringing I have heard with other Cobras. He also had some popping going on and needed some tuning. I'm happy to report that my Cobras, sans baffles, don't ring and have a really throaty sound to them. Comparing the Shadow Aero with hole saw mod the VT1100 with unbaffled Cobras? No comparison. The Aero sounded like it wanted to be like the VT1100 when it grew up.
Personally, I'd give the same advice a lot of folks gave back then. If you want the sound then put on a set of aftermarket pipes. Save the stock units as is in case you want to go back. Ride it awhile and if you decide you are sure you are going to stay with the aftermarket pipes then you can sell the stock pipes to all the folks who did that hole saw method then wanted to go back.
I'm not saying the hole saw is bad or that it sounds like crap. I liked it well enough, but it was never going to be a substitute for real aftermarket pipes.
I was going to see if I still had a short video of the Aero pipes right after hole saw but Photobucket seems to be having issues at the moment.
La vida está en el viento. (Life is in the wind.)
RIP Miss Andi. It was a good and long run old pup.