My favorite text editor, UltraEdit, unfortunately only runs on Windows. I have found Kate to be a suitable replacement, but it is not nearly as powerful as UltraEdit.

The first feature I miss is regular expression replace--I have a feeling that the feature exists, it's just that I haven't been using Kate correctly. As you probably know, Kate offers regular expression find. But it doesn't seem to offer regular expression replace. For example, if I check the Regular Expression option, with
I just get the literal \n, as though I had typed in \\n instead (\\ being the escape sequence for \). Similarly, other escape sequences don't work.

In a similar vein, regular expressions--at least its implementation in UltraEdit would allow me to do something like...
This would switch foo bar with bar foo.

UltraEdit, however, is limited in its regular expression capacity. It does not allow for quantifiers such as {3,}--a feature I hope to eventually see in Kate some day.

The second feature that I miss are column edit--by which you can select an entire column of a text file, instead of a row. It allows you to, for instance, add the <li> tag in front of all items of a text list if you were to convert it to html. Or to add tabs in front of a series of selected lines to clean up your code.

The final feature is find and replace capacity for all open files. Often times, I might have, for instance, a bunch of HTML files whose HTML tags I want to strip. I just do a series of find and replace to remove the HTML tags, the comments, and the escape sequences and enter the proper white space for <p> and <br>. Granted, there are other ways to convert HTML to text, but find and replace all open files comes in handy for other reasons as well.