Hi Susanne,
I have to reiterate all that has been said before....expensive to set up (gun, tips, glue itself, the mistakes that you make!!), can come off early, but good stuff, all in all!
Fascination drove in front shoes made out of Superfast for about 2 years, I think, and now has glue on shoes (Epona shoes) that I glue on with the Superfast. The most important thing is definitely the hoof prep. Best for me has been: right after a trim (not even let out to walk around), alcohol to dry, and then a blow dryer to really dry out the hoof. With that, I can get about 4-5 weeks out of a set of glue on shoes--ones that are getting a lot of work and torque from driving. Without....well about 2-3 weeks, probably. Also, if the horse is standing around in moisture and wet, the time on the hoof decreases dramatically. But during the summer, I can be pretty sure they will stay on for as long as I need them too.
Also, the traction on pavement/wet grass isn't great...I wouldn't say any better than barefoot, and possibly worse. On dirt, dry grass, its great!
I've just started using the SoleGuard this fall on Peeks (Prelim mini), as well as on a morgan that I have been competing barefoot in CDEs. The morgan had transitioned from wearing shoes all his life to barefoot in the spring, and was consistently a little sore on hard ground/trails, so he needed some protection while getting used to his 'new' feet. The soleguard was amazing for removing tenderness! He moved out very well with no hesitancy on rocky surfaces...in fact, we won our marathon on a track that was fairly hard with some rocky patches. However, in one of the hazards that had wet grass, he did have a pretty good slip. I think there is less traction with the soleguard than barefoot, which makes sense when you look at the bottom of the hoof with it in. I think it lasted about 2 weeks....even with doing the prepwork beforehand. However, Peeks' filler lasted about 4 weeks. So I am unsure as to how long it will last me on average. I would definitely suspect, though, that wet conditions will decrease the length of time it will stay in.
Bottom line: they may or may not work for you! I've found that it takes more time and effort (obviously) than just barefoot, or even traditional shoes, but, it's what I have to do for my horses.
ETA: Wanted to add a link to a picture of the morgan as he is competing at the Shady Oaks CDE (see the gravel leading into the water and out of it? No problem!), and one of Peeks with Superfast-glued shoes on.
http://i2.photobucket.com/albums/y3/MiniHGal/IMG_0672.jpg
The morgan
Peeks: