No, in my opinion they are not "ok", and I have shared that view everytime someone asks!
If you have money for a deposit - you will risk losing it if you don;t buy the home....that's right - it is non-refundable......if you don't have money, you will (usually) be asked to pay an amount of rent OVER and above the normal rent - only that overage would be applied to the purchase, but forfeited if you do not, or cannot, buy the home.
I think a lot of consumers mistakenly think all their rent is applied to the sale, and they can simply decide not to buy the house, get their money back, and walk away.
it really doesn't work that way in a rent with the option to own situation.
You are paying for that "option" - the right to walk away.
The advantage is on the seller's side.
If you are having financial issues now, you really should work on them before looking to buy a home - even if you could find this sort of deal.
There aren't many of them, because most sellers who want to sell, and CAN sell (they aren't upside down on their mortgage) ...will sell now, not a year or 2 from now.
Do yourself a favor - protect your assets - work on strengthening your financial position, and then buy a home in the normal fashion when you will have a full selection to choose from.