First, many thanks for this contribution; it's great, that the re 
module gets updated in that comprehensive way!

I'd like to report some issue with the current version 
(issue2636-20090804.zip).

Using an empty string as the search pattern ends up consuming system 
resources and the function doesn't return anything nor raise an 
exception or crash (within several minutes I tried).
The current re engine simply returns the empty matches on all character 
boundaries in this case.

I use win XPh SP3, the behaviour is the same on python 2.5.4 and 2.6.2:
It should be reproducible with the following simple code:

>>> import re
>>> import regex
>>> re.findall("", "abcde")
['', '', '', '', '', '']
>>> regex.findall("", "abcde")
_

regards
    vbr