Easy to swap quality filters. Only downside is the lens cap will take the filter off when you remove it (if you put the cap over a filter on your lens), but other than that, I love the ability to throw filters on and off quickly. I can also use my older screw-on filters on top of these, so I can stack a magnetic CPL, magnetic ND16 and a screw-on ND1000 for a long exposure shot (as an example).
They are very good quality with no more color shift than any other filter on the market.
Also as a tip, I bought the largest filter I needed and bought the freewill step up rings for my other lenses. This way I only needed to buy one set of filters. The step up rings from Freewell have the magnetic base built in.
One last thing, the filters now come with 2 base rings, one with a UV filter and one that is just the open ring (no glass).
When I received the ND filter I could not get it to work right with the open base ring that I attached to my lens. Then I noticed the UV base ring was already attached to the ND filter in the package (they are so thin I could not tell), so I was trying to attach one base ring on top of another, so I just separated the UV base ring and put it away and viola the ND filter fit perfectly into the open base ring. I do not like putting extra glass on my lens, so I dont use UV filters.