When I started to use OSX, one of the first things I looked for is a good editor. On Windows, the sheer number of choices (and there are many good ones) can be overwhelming. The competition on the Windows world is fierce which has helped to weed out the weak. What I found on OSX was that the most mature editors were the result of Apple using the BSD kernel and thus able run Unix editors such as EMACS or VIM and when it came to advanced IDEs, they were ports from other platforms such as Eclipse.
There are some native-OSX editors such as TextMate (commercial), Smultron (open source) and BBEdit/TextWranger (commercial), but while its users tout how advance they are, they are still behind what is available to Windows programmers. Features such as pretty printing, snipplets, split-screen views of files, etc. are either non-existence or just starting to get introduced to the Mac world even though they've been there since the days of DOS. It can be argued that those feature aren't needed and I'll admit that a lot of features I only use once-in-a-while. However, the decades of work that has been put into them has allowed them to be part of editors without being intrusive and when I need them they are there.
As a Windows/DOS and Linux user, I've been spoiled by these features and it surprises me that Mac developers not only do not have these, but that they don't even know they exist.
For those interested:
#1 Visual Slickedit (commercial)
#2 UltraEdit (commercial)
Notepad++ (free -- I'd rank it #1 free editor)
#1 Visual Slickedit (as a general purpose IDE)
#2 Microsoft Visual Studio (Linking to the free "Express" edition)
I'm not sure yet... I'm going to give Smultron a try and I've been using TextMate on-and-off at work.