Differences between sed on Mac OSX and other "standard" sed?

I am having some issues in using an answer provided on this site for [this question about a sed command to replace a blank line with two other lines of content](https://unix.stackexchange.com/questions/13688/sed-command-to-replace-a-blank-line-with-two-lines-of-content) , and it was brought up if the sed command on Mac OS (10.6.7 for me) is different. I don't think that it is, but was wondering if others on this site thought differently.