RegExs...fun to figure out and to write the first time. Pain to debug and supports x-number of months in the future, especially by other developers on anything more than the common cases.
There are some things that can help with this:
0. Consider whether string.split could do part of the job instead.
1. Consider writing unit tests for your regexes.
2. Split your regex onto multiple lines.
3. Turn on the option that lets you include comments inside your regex.
I do agree that really complicated regexes get to be a pain.
I try to assuage my pain and that of my devs by actually....commenting the REGex. The comment explaining things is often longer than the regEx, but helps quite a bit.
I think this is a pretty useful idea.