You get through immigration faster,but that's basically all. You're paying a lot for a visa just because you haven't reached 50 years of age.Imo, a waste of money since the DTV was released.
The 90 days report is free. After every arrival you need to do the first report in person. Following reports can be done online as long as you're in country. You must submit the TM30 within 24 hours after arrival.
How did you think it worked between agents and immigration? Every agent pays immigration for the service. The only thing that's borderline not ok (at for example Bangkok Bank) is the 800k transfer to your account.