Sed Messed Up on OS X?

While trying to further my knowledge in unix/shell programming I’ve found that the unix command sed is messed up in os x. I think the problem is that the GNU/linux versions of some commands are different that the Darwin/BSD versions, this might be obvious to you linux/unix gurus out there but to me this is new news. I always assumed that the functionality in the commands on os x and most linux variants were the same.

In any case, I downloaded the GNU sed source code and compiled a nice fixed sed command for myself (After I compiled it I found out you could of just easily gotten GNU sed through fink-commander. :P). Walla, the newline problem I was having with the mac os x version of sed was fixed.