I've shot one and they do shoot sub-moa at 100 yds.. 20ga may be a bit more popular than the 12ga, but it's personal preference.

Do you need it? Nope..... I'm sure you kill lots of deer with you H&R slug gun.. Sub-Moa is only imortant when planning on shooting longer distances and since I would never suggest shooting your slug gun over 150-200 yds then at 200 I'm sure you can still shoot a few inch group with the H&R which is accurate and lethal on a whitetail.

BUT, if your like me and you want your guns to shoot thebest possible then something like this is really awesome. I've thought it for a while but I have a list a mile long of guns I want and this one just happens to be down the list a bit.
Do ya need one, No... Do ya want one.. Oh Yes....

It's a very cool gun and I personally think it's worth the money. No different than buying an Ed Brown Custom Rifle to take to Africa.. The ammount of research and work that goes into the gun saves you all sorts of question and you could not build the rifle yourself for that money unless you were a custom gun maker.

If ya got the money and nothing else is on your "list" then I say go for it. Post some pics of your groups too...