locale and performance?

Hello,
in the documentation is written that there'a a perfomrance impact if
another locale than C or POSIX is used.
problem is that using the standard locale results in unusable order
results for languages with spcial chars. in my example "umlauts" in
german.

it isn't acceptable to use the database without indexes if another
locale is used. are custom operator classes as described in the manual
as high-performance as the native index? are there any examples how to
use them in my case?

are there any tests that show how the performance decreases if another
locale is used? why is there a perfomance impact? it's a disappointing
that postgresql is only in one configuration to suply the max.
performance.

any tips or hints on that?

regards

Daniel