According to http://confluence.atlassian.com/display/JIRA040/Performing+Text+Searches?clicked=jirahelp#AdvancedSearching%28newdraftfor4.1%29-EscapingSpecialCharacters%3A\ it should be possible to search for a special character using an \ escape prefix. But in reality, it isn't.
For example, if you are interested in finding issues with [ in the summary, and in the simple search querying for
- nothing comes back.
Switching to advanced search presents you with
and there is no way to edit this query and make it work.
Using JQL escape syntax doesn't work either: