I had one through one of the group plans that my parents set up. I got a lot of mloney out of it and have no complaints. I signed both of my kids up through them as well and the points above are valid about the fees being front loaded. If you ever wanted to get out of it after a couple of years you can put the plan on hold. I plan on staying in as I'm sure everyone does, and in the end my kids should have a good chunk of money for school.
Going through a financial advisor is fine as well. For my second child I looked at both options to see which paid more historically and the cost of fees. Banks and financial companies dont take their fees the same way, but they definitely take them. You just don't know about it. Either way banks, Scholarship Trusts, Financial Advisors, they all get paid, and so do you and your kids. 20% on your investment is pretty good from the government, plus whatever the fund does over the 17-18 years. It is a great idea for your kids if you can afford it. How you do it is a personal choice based on having all of the information you can. I had my financial advisor come in and had my Scholarship rep come in and asked them why they were better than the other and in the end I didn't see much difference over the long haul which is what everyone should be looking at. If you arent in a stable job than banks are probably better in the short term.
Contact a rep from each and see what works best for you.