First of all, I take mine diluted in olive oil, which is much safer. This is potent stuff. I think people who have the strong reactions are taking the full strength stuff, and I don't think it's a good idea. I get a little warmth at first, but NO BURNING. I think that's a good idea. So, if you have getting a bad reaction, try moderating your dose. I use 1 part OoO to 4 parts olive oil, per the Wolfe Clinic.
http://www.thewolfeclinic.com/oregano.html
In brief:
Oil of Oregano is a potent anti fungal, anti bacterial, anti viral, and anti infection substance. If you have problems with yeast, it can kill the yeast, but may create "die-off" symptoms, kind of like flu. Backing off the dose until it is killing yeast at a level where your body can get rid of the toxins is the recommended way to handle these symptoms.
Unless you are sensitive/allergic to it, it doesn't seem to have any other side effects. I can't say it made me lose weight, exactly, since I was already working on a somewhat indulgent summer. Nor did I have any yeast problems that I knew of. However, it did WONDERS for my rosecea, and I added 4 full strength drops to my shampoo, and it cleared up a little bit of flakes, so I am a believer.
Also, I had taken two full courses of antibiotics this summer, and OoO got my missing energy back. I think it's a great tonic, but I would take it for the complexion situation alone.
Most sources recommend two weeks on, two weeks off.