I wouldn't be concerned about WildFire, it's an indipendant application, I would make sure where you put it is secure and with the right permissions and the program is set up as secure as can be... My concern is (I assuming) you using a pre release candidate for a production server at your work...
A lot may change between now and when the full blown here it is release comes out, and if it's drastic or something drastic is found out, you may be stuck with doing everything your planning on doing all over again.
JMO - but a pre release is not meant or made for production - testing yes - production - no.
I like the features that are being worked on in 7, and when it's out in a full release version, it will most likely take over mail / web site / proxy, but not until a full release is out, I have 80 +/- users, 3 buildings in two different states and an owner that hates it when he can't get his email.
That's just my "scary scenario"
