ß (eszett) and regexp trouble

[Memnon Anon]

Hi,

I just noticed an inconvenience with regexp searching and the ß char.

Try this: C-M-s (isearch-forward-regexp) with [[:lower:][:digit]] 
now:

        This is a sentence. All lower chars (like abc or ß !) and 
        digits like 123 should be matched.

Well, ß is not matched.

I found some info regarding that problem, e.g.

http://lists.gnu.org/archive/html/emacs-devel/2009-11/msg00460.html

Yes, ß is problematic (no uppercase version, should be replaced with
SS, but not all SS are ß etc. etc.), but I have to guess german emacs
users must have figured out what to do about this already.

So, what do you do?
Do you use the uppercase ß char in your standard-case-table?
Do you suffer from performance issues doing so?

tia,

Memnon