I have shot them for over 25 years and taken 150+ animals without a single failure. When properly set up they have a very minimal impact on accuracy. In fact, I make no allowance for them when shooting. Again, proper set up is critical. Most every malfunction with a strong tracker can be traced back to shooting it right out of the package without pulling 300' of line from the spool before using.
Again, the single most common mistake made is shooting it right out of the package. This causes significant arrow drop and confidence issues that will not occur if you do it right.
We have recovered countless deer, bear, turkey and hogs that traveled great distances without bleeding due to the trackers. They are a valuable tool when used properly.
Here is a video that can help with setting one up.