Had the ws replaced once on my E46 Coupe due to a crack forming because
of a stone strike in the black lower left area of the ws.
Absolutely no problems - the insurance fully covered it without a peep,
even after I INSISTED that it be done by my preferred BMW dealership
AND that they used OEM glass. (Incidentally, they did a flawless job -
afterwards you could never tell the ws was not factory fitted.)
My advice to you:
1.) Have it done properly by your preferred dealership - they said they
do 12 ws-replacements a week at mine, so no big thing for them. I let
them keep the car overnight to ensure the bonding had sufficient time
to fully harden before ever moving/flexing the car.
I'd strongly advise against having it handled by sock-puppets like
carglass or one of those jocks who comes and does it in 15 mins in your
company parking lot.
2.) Make sure you get an OEM ws fitted - especially if your BM has the
rain/light sensor and/or you have the 'climatic/tinted' ws option.
3.) If in some way you're not insured for ws replacements, still take
the trouble to have it done properly. Might be more expensive, but this
is something that could cause you much misery in the long run.