I use my own merchant account and also use paypal for my online store and client payment system. At first I didn't want to use it because I felt that it made me look unprofessional or like a small player when bidding on a big contract with corporate companies. But, I was surprised how many orders and clients pay with their paypal account. I wonder how many orders I would have lost if I didn't have the paypal feature on my sites.
I don't have the paypal debit card and do keep my money there and use it to pay for other items on ebay or things I find on the net. I have never had any problems with it.