Fortress anchors work great and are lightweight. They DO require a length of chain on them, but that is highly recommended for ALL anchors. Chain gives a bit of "gravity bungee" effect.
I personally use a large galvanized Danforth fluke anchor with no chain, A medium sized econo Hooker fluke with no chain, and a large CQR plow anchor. All of them work great as long as you set them properly. I've never had any of them come loose by themselves (except in smooth rock bottoms - which we ain't got around here).
I'm sure everybody has their own preference for setting anchors, but I always run far uphill from my target resting place and throw er in. I then back downhill from my target spot, letting out scads of line. I then tie off and set her hard. I try to go WAY past the 7:1 rope:depth recommendation. After she grabs then I pull back to my target spot and tie off. If I don't want to rotate, then while I am "back" I'll throw off a smaller secondary anchor and pull forward of my target to set it also. Then pull back and tie off.
One of my regular spots I have put a chain on a big tree on the point. I drop the anchor on the cruiser out and back up to the tree. I put a 30' line off the stern to the chain and use the windlass to set the anchor. The Windlass is rated for 3000# of straightline pull. I bog her down real good.
Held fine in a storm with 65+ mph winds (tornado less than 1/2 mile away). Was a bit concerned, but it never flinched.
I see too often boats dropping nice anchors and staying right on top of them. I hear gripes about the anchors not holding, but these guys never give them a chance to hold. Sometimes they snag a stump of something so they just think their anchors are crap and only work half the time. You just can't teach these guys.
I think, though, that the light weight benefits of a Fortress aren't all that great if you don't use a chain. You'd be better off with a galvanized anchor that you can wrap in a towel and stow. (I don't like the idea of all that chain rattling around while jumping waves either).