I've tried the freeware editor NotePad++ [
^] (open-source, GPL License, uses the Scintilla edit engine), and I've tried the commercial program SublimeText [
^] (US $70 license per user, I sampled the trial version only, but assume it has all the features of the for-sale version).
I settled on purchasing UltraEdit [
^] (US $80) for many reasons: it's a one-font-only editor with an astounding range of features ... useful for so many purposes; it's one of the few programs that is always running on my dev machine.
Customizable color-highlighting for different languages available, ranging from C# to Ruby, Perl, Python, XML, etc. Every element of the UI can be customized to your taste, or you can switch between "modes of use" that are pre-defined by UltraEdit like "Power User," "Technical Writer," "SysAdmin," etc.
Also has macro recording, and scripting available.
My recommendation is that you try all three of the programs I mentioned, and see which one best fits your needs, and your budget.