I bought one, here are my thoughts:
1) If I raise my arms up over my head, some of the underarm magnets will come loose - not that big of a deal as lowering your arms will usually cause them to snap back into place.
2) Because the sleeves are held on with magnets instead of zippers there are gaps between the fabric pieces which means that wind/water can get in under the right circumstances. The back of the jacket/vest portion already has a vent, so it's not like it's intended as foul-weather gear anyway, but it's something to be aware of so you're not surprised.
3) There's a pocket just for the sleeve piece but once you've folded that piece and stuck it in the pocket, it makes the jacket feel lopsided (probably because of all the magnets)...I'd have preferred if the pocket had been positioned in the middle instead of on one side.
4) No zippered breast pockets on the outside of the jacket - that's where I like to carry my wallet so I was rather disappointed about this.
On a scale of 1 to 10 I'd give it a 7...I like it, but not as much as my other SeV gear.