basically it works pretty good but not for everyone and people tend to like the plastic guide ones like MRP or E13 a little better. But those that have theirs adjusted perfectly like them. Something like that.....
I've got one - a seat-tube mount one - and it works quite nicely... I used to drop the chain on my 1x9 on rocky stuff not quite once a ride and now I just ride and have not dropped the chain once since I got it...
"You know how they make aluminum bike frames? They take steel and suck out all the soul..."
I have one. I think you really need a spiderless crank to make it 100% bullet proof. I mean, I still get dropped chains every now and again because the cage doesn't sit low enough over the chain. It is still far better than the guideless set up.
"Bikes aren't fast--people are fast. Bikes are overpriced. It's an important distinction."---BikeSnob NYC
@GrantB - why do you need a spiderless crank? How does that impact where the guide sits?
You don't have to have a spiderless crank, but if you do, the guide can fit down closer over the chain. With a crank with chainring spiders, the guide will hit the spider on the outside of the crank before the guide can come down as far as it can over the top of the ring. Especially on the smaller rings like 32 tooth rings.