When you finally get the reviews of your NSF proposal, they will have ratings, Excellent, Very Good, Good, Fair, and Poor. Some may give you between two, like E/VG, or G/F as if there was some sort of illusory precision to these categories. Some might decline to rate, wanting their comments to stand on their own.
The point of the ratings is to give others an indication of how serious you think the problems with the proposal are. Yes, nearly all proposals have problems, in the eyes of some or all. I know that even with our best proposals, there are things I wish were better.
They also give an indication of the strengths of the proposal. If you give a proposal an excellent rating it is important to specify why you think it is so great, to counteract others that might quibble.
Because everyone knows how tight funding is, reviewers tend to give very few Excellents. In panel it was common for people to announce that they only gave 2 excellent votes out of their 15, and this was one of them. It was an argument with some weight.
I tend to generally stick with the top three categories, understanding that a Good in this climate means the proposal will not be funded. I would give lower if the proposal was very lacking, not fulfilling the basics of the process. But I don’t want to discourage the scientists. I want them to work hard and feel that what they are doing matters, even if it can’t get funding this time. Many reviewers stick with the top three categories, but others don’t.
Whatever ratings you get, focus on the comments. Even if you get funded, you could get useful advice for improving your study. If you don’t get funding, this is the first place to turn to learn what to change.