Here's another inconsistency (same setup as before, running issue2636-20101029.zip code):

$ cat test.py
import re, regex

text = "\n  S"

regexp = '[^a]{2}[A-Z]'
print re.findall(regexp, text)
print regex.findall(regexp, text)

$ python test.py
['  S']
[]


I might flush out some more as I excercise this over the next few days.