I am a staunch vi user myself, but can't quite manage to call it an IDE, it kind of lacks the Integrated part. but that might depend on what you want for integration. There are some nice plugins for CVS and DB develeopment, and even ones that claim some IDE capabilities such as project grouping and buffer display lists.

I have used Komodo and find it a very good IDE alternative, especially it's regex builder, but I still find myself using vi commands and adding control characters all over my code.

I tried Eclipse and still don't have a good opinion on it. Supposedly there is a vi plugin for it that I wouldn't mind trying, but although I know Java, it still gives me a rash to think of building my Perl apps in Java.

I have also tried using one called PIDA. It's a python app but allows you to choose between several editors including vi. Of course if you don't use vi, none of this probably matters to you.