Pros:

1. Ability to remove scope for cleaning.

2. Ability to carry a backup scope on an expensive outfitted hunt (in case the airlines break your other one).

3. Ability to use multiple loads per gun with just a scope change. For example, you coul have a hot fast load dialed in with one scope for hunting open fields and a slower load with a lower powered scope for hunting brushy areas all with the same gun.

4. ? These are the uses I can think of, there may be more.

Cons:

1. POI shift if not remounted correctly. Also cheaper QR rings will not return to zero. I've never had the Warne Maxima Quick Release rings fail to return to zero.

2. Cost. A good set will cost more than an equivelent fixed ring.


Conclusion:

I use em on all my muzzleloaders. Warne rings and bases on 3 of them and Leupold QR (the ones with the posts) on my ML pistol. I've been using them since 2002.