[Dovecot] linux 2.4 vs 2.6 kernel

hi I read ( I think in dovecot wiki) that ext2 or ext3 fs on a 2.4 kernel can get slow due to the number of files in a directory. Does anyone know if kernel 2.6 has similar limitation? I'm not at that point now, but before the box goes live, I'm wondering if I should resolve that. Glenn