I don't think it would mean much coming from a grad student. For one, everyone will know because you are likely closer in age and position, you are more likely to be drinking buddies with this guy. Second, he might not know how to write a strong LOR even if he is trying to do so. There is a proper language that adcomms and professors understand on how to write these things. At the very least, you could have him write it with his boss signing off on it.