I think that this article is a nice start, but I wish that there was more information about the symptoms of these problems. I've had two implants, one of which was rejected. I preformed quite a bit of research in order to prepare for my surgery and while I read that there is a risk of rejection, none of the articles I read discussed how that rejection manifests itself.
I formed an abscess higher along my gum line and didn't notice it initially. Once I did notice it I thought it might just be due to swelling in the area - I had no idea what an abscess even was before this. Because it didn't cause me any pain, I waited until my next appointment with my dentist. Some months and several antibiotics courses later I still was not able to shake the infection and the implant had to be removed.
I think it would be nice if there was more information out there about what to watch out for in addition to what can happen. There is so much "going on" in your mouth after a serious procedure it can be a bit difficult to tell what is worrisome and what is normal.