Like Jeremey, I too have been using Paypal for 5 or 6 years and not encountered ONE single problem. Of course there will be people saying otherwise, I will put a bet with you that for everything good you can find written on the internet, I'll find something bad written about it too! That's the joys of the world wide web! There is no such thing as a product or service that will please everyone.
Ignore what you have read and feel free to use one of the best merchant systems on the market today.
Don't aim for success if you want it; just do what you love and believe in, and it will come naturally.