If you hold those investments for long-term, 18-year is not long enough; If you like to do some short-term tradings, it allows only 1 transaction per calendar year.
There are some workaroud for 1 transaction per year limit though, you can temporarily change beneficiary to be able to do another transaction, but awkward nevertheless.
And tax advantage is somewhat similar to ROTH IRA, your after-tax money gains tax-free if you use it for higher education. But the pretense is that you have to make money, or else you don't even get to take capital loss deduction...
