When coding, I currently utilize the following:
-webkit-border-radius: 4px;
-moz-border-radius: 4px;
border-radius: 4px;
After running tests, it seems that there was no noticeable difference in modern browsers (Chrome 33+, Opera 25+, Safari 8+). Internet Explorer 8 does not support this property, but the vendor prefixes do not seem to have any impact.
Is there a valid reason to keep using them?