As soon as a hot, new restaurant opens, there is a rush for food bloggers and online reviewers to dine there and immediately report back. Time is of the essence, with many wanting to be one of the first to review the new place. Often, they will eat there once and then post their thoughts. If they enjoyed the experience, they will likely return but if they didn't, then they probably will never go back. Such reviews might do a disservice to these restaurants, failing to take into consideration their newly opened status.
Opening a new restaurant is an arduous and expensive task and there is only so much advance planning that can be done. The true test is when the restaurant finally opens to the public, and then the restaurant might see certain problems and errors that need to be resolved. As such, I think a good rule of thumb is to allow a new restaurant about three months to fix all of the initial problems. That should give them sufficient time to identity and resolve the initial kinks that often plague all new establishments.
What that means then, is that anyone reviewing a restaurant during that initial three-month period needs to give some leeway to the place, to not judge them too harshly. Any negative issues that a reviewer finds might already be on a list to be fixed. So you cannot assume that those problems will continue to exist in the near future. The restaurant deserves the time and opportunity to resolve any initial issues.
There is nothing wrong with reviewing a restaurant during the first three months of its opening. But, how you review the place can be an issue. I usually preface my own such reviews, noting the newness of the place and that any problems I encountered could very well change once the initial kinks are worked out. I then try to return to the restaurant, once that three months period is over, to see what changes have been wrought.
But I have seen some bloggers who strongly criticize a new restaurant soon after it opens, and then never return. They rush to judge, without allowing the restaurant a fair amount of time to rectify any initial problems that are found. They do a true disservice to new restaurants as well as indicating their own lack of professionalism. Being first to review should not be their primary concern. Rather, they should be concerned with being fair to the new restaurant, being fair to the owners, chefs and staff who are working hard to make their new place successful.
If you are guilty of these offenses, then endeavor to change your ways. You can still review a restaurant soon after it opens, just measure your review with mercy and be prepared to return again, after at least three months, to see whether the restaurant has changed or not.