As I've said elsewhere, I've got eleven of them.
There were complications with one; it didn't "integrate" and came out when force was applied during installation of the abutment. That required time for recovery (three months or more) and a second one was installed.
A second set of three required a bone graft to provide enough foundation for the implants.
A third one became infected when implanted; it had to be removed, and a four-month healing period was needed before the second installation could be done.
Right now, though, all of them are functioning, and it's pretty much as though I had my original set of choppers.
If it weren't for the time-consuming nature of the process (and the cost!) I'd recommend it over dentures wherever possible.