I have used it and it does work. When I got my OTTB he had ulcers, so I used this everyday for a month. You will begin to notice improvements after about a week of use though, but need to keep up with the treatment for as long as you are advised to from your vet.
You will also need to think about your horse's current management and may have to change a few things. Free choice hay/pasture, high fat/fibre feed rather than grain based, lots of turnout time, maybe rethinking your training/showing schedule to be a little less stressful, etc. Speak with your vet about this.
If you go through with the treatments but do not change your horse's management they are likely to recur. They can recur in times of stress as well, and there is a lower dose form that you can use in times of stress, like a big trailer trip and show that will help. Again, speak speak to your vet.
Hope this helps and your horse is feeling better soon.