Victor,
I have not tried "Casino on Net" but I have spent many many hours and many many $$ playing on "Lucky Nugget.com". I have never had a problem with any transactions with them. If you cash in any amount up to your total buy-ins they simply credit your credit or debit card for the amount of your cash-in. On the rare occasions when you cash in an amount in excess of your buy-in you must notify them of how you want your money to be sent to you. They give you several options but will not simply credit the card that you have on file with them. It does take a few days for the money to be refunded to you but like I said I have never been screwed by them.
One interesting note is that while you are waiting for your money, they make it very easy to reverse your cash-in. A simply click of the mouse and your request for money is immediately stopped and the amount shows up as credits available to gamble with.
LuckyNugget.com (I assume they all do) does give you a monthly rebate or comp based on your level of play. Additionally they frequently send you an email telling you how you can claim "free play" credits usually tied to holiday or other promotions.
I have found that they make it way too easy sit in front of your computer in your underwear while you are loosing your shirt.
My recomendation is DON'T DO IT!!