The detriment is the lack of opportunity. gTLDs will become standard for the people who can pay for them and ordinary folks will be stuck on subdomains of conventional TLDs. Above all, it's an example of ICANN prioritizing money over a free web and the wealthy over the poor. No company that does that should have any control over the Internet.

New happy hunting ground for scams, phishing, typosquatting, etc.