It actually happened today!! Vacuum failure in IMC.

Departed Asheville NC today into IMC enroute to Columbia SC. Well into
IMC and about 6500 MSL the DG started to slowly just start rotating and
the AI started to lean over. Backup vacuum-no help. I couldn't
believe this was happening in IMC; I only fly it about 5% of the time.
Columbia was just a bit above minimums. I was not prepared to try an
ILS with no operative DG, and most of the GPS approaches at CAE want a
WAAS capable GPS, which my G430 isn't.
Bit the bullet and dialed 7700 and declared an emergency. Asheville
approach offered a no-gyro radar directed approach back into AV which I
declined, since the mountainous terrain was not an attractive option in
this situation, at least to me (even though I live in Montana). They
gave me vectors to Charlotte, at my request, since it had similar
weather, but friendlier terrain. As I was descended into CLT I saw a
huge hole and an airport just below. Told CLT approach I saw an
airport and could descend visually to it, and since I seem to have read
somewhere that it is best just to get on the ground ASAP in this type
of situation, said that I just wanted to land there. They gave me the
name and ID of the airport (Shelby NC), and I landed without incident.
Lessons learned:

1. Keep up on your partial panel skills. Do not underestimate the
utility of the turn coordinator (or needle/ball).
2. Carry something to cover the failed instruments; they will distract
you. (Fortunately, I had covers.)
3. An STEC A/P which runs on the TC, rather than the vacuum
instruments, is the way to go.
4. If you have a good a/p and coupled GPS, they can fill in very well.
5. Don't be afraid to declare an emergency, and accept their help.
ATC at CAE, Greer (sp?) approach, and CLT approach were ultra
professional and very helpful.

I'm not a highly experienced instr pilot, but stuck with what I've been
trained to do, kept cool (I hope/think), and "dealt with it".
Now, for the paperwork.