mcbammer,
Don't worry about the ATF, only gets confusing if you are switching back and forth between rifle and pistol. If you want to do it, best to get more than one and designate one a pistol the other a rifle. That's what I do.
As to pros: switchable barrels, multiple configurations as to stock type, (thumbhole, synthetic, walnut, laminate, etc.), I think I have about 6 or 7 barrels for my rifle. I use a Contender for a pistol and have about a dozen barrels for that. With only one receiver, once that trigger is tuned in, it doesn't change like when you switch complete rifles. Takes up less space in the safe.
Cons: basically all the above, lots of combinations can get confusing. It is addictive
As for price, a complete rifle would set you back about $400 to 700 depending on the specific model you get. After that barrels range from $150 to 400, depending on manufacturer and type. And don't forget you can add muzzleloader and shotgun barrels too.
I guess I'm a little pro encore/contender.
bull