[exim] FreeBSD ffs vs. ufs?

Hi Exim Folks,

I'm currently doing some performance tuning on a pretty heavily used
exim server we have here. We're running FreeBSD 6.1 and am noticing
the disk loading to be quite high. The filesystems are currently
configured as UFS however i'm contemplating using tunefs to switch
them to FFS with soft updates enabled.

I was wondering if anyone had any positive or negative experience
with using ffs+soft updates with exim on a FreeBSD system? I
understand the risk of losing data in the event of a power failure
(soft updates not being written to disk immediately). I'm just
wondering if there are any other gotchas that aren't immediately
obvious.

Cheers,
Marcus