1. The vast majority of individuals would not need to spend any time filing taxes or thinking about taxes.
2. The VAT would extract revenue from tourists and folks whose income is "off the books". That's money we're currently leaving on the table, so to speak.
3. Since fewer people are filing, it becomes much cheaper/easier to enforce compliance.
4. Businesses will have to deal with the VAT, which is extra work, but they'll no longer have to worry about corporate income tax, deductions, depreciating assets, etc.
5. Since employers no longer have a tax incentive to subsidize their workers' health insurance, most would probably stop. That's a feature, not a bug. If everyone in white-collar America is forced to purchase insurance on the open market, I suspect there would be much more openness to health care reform.
6. It would become much more expensive to live in the U.S. as someone who isn't authorized to work here. No need to build a wall; people would self-deport. Mitigating factor: I'd make it easier for those outside the U.S. to become citizens or legal permanent residents.
7. The large-ish estate tax is designed to make up for the fact that this plan is generally more favorable to the wealthy, the majority of whose income is capital gains.