I have. Rained like mad at the autocross school I instructed at Sunday. The Elise ran great in the instructor portion and I gave maybe a dozen students rides, pointing out the line. Since my rear Star Specs are pretty thin, oversteer threatened, and I gave one of them a thrill ride with a full spin.
A little windshield washer now and again helped out on the way too and from. Michelin blade still working great since 2010.
I feel so lucky that my hardtop does not leak in a pouring rain, having seen some of the horror stories on here (furriously knocking on wood).