As a Before & After comparison (although I already knew the answer to "Is it worth the money?"), a couple months back I did baseline shooting with 13 different buckshot loads and three different slugs through a standard Remington 870 PMAX with 18-inch barrel at measured distances. After which I sent the barrel to Vang for his package on it.
Then I repeated the baseline loads in the Vang Comped barrel.
Most emphatically YES! It IS worth the money.
Buckshot patterns tightened markedly, in some cases dramatically.
Recoil is lessened (slowed down is a great term

) with the internal modifications, making even three-inch shells more bearable. Vang says reduction is about 15%, I have no precise way of measuring it, but the difference is notable.
The ports reduce cheeksmack in holding the muzzle down during recoil.
Slug accuracy (three tested) declined slightly after the barrel work was done. Figured that was a fair trade, since I mostly intend for my 870s to be used as true shotguns anyway.
The PMAX had sights on it from the factory.
I have apertures on all three of my Remingtons, for me they work.
LPA rears are easier to adjust than the Scattergun Trac-Locs.
I have mag extensions on all three, I prefer as many rounds IN the gun as possible, I've given up on the sidesaddles OUTSIDE the gun.
Your choice on the extensions.
A good recoil pad is critical, and if your significant other may be using it, you should consider shortening the stock at least a bit to a good compromise length between the two of you.
Denis