I've been using PayPal for years and personally I'm happy with their service. If you have a large e-commerce business with huge sales volume you can save money by using bank merchant services on your site. However, PayPal are ideal for handling online sales of low to medium volume and their fees are generally less than you can get elsewhere.
Based on other posts you have made about your business I would suggest that PayPal is the best option for you. But you are absolutely right to look at alternatives to see if they can offer you a lower cost solution.
Have you looked at
PayPal's fees page to ensure that you are on the best rates for your business? Depending on the level of business going through your account, you can sometimes apply for a lower fee level - I believe it's if you are doing over $3,000 per month, but check the link for your own circumstances.
If you are looking for other payment options have a look at the links below;
http://aws.amazon.com/fps/ - A relatively new service from Amazon
http://authorize.net/
http://www.rbsworldpay.com/
https://www.alertpay.com/index.aspx
http://www.sagepay.com/
http://www.moneybookers.com
http://www.2checkout.com
Good luck with it and please do let us know what you decide and how it works out.