My instructor and I flew from Phoenix to California to try an approach in real IMC for the first time (for me), and when we got there weather was far worse than expected/what was shown and briefed. Shot a LOC (where I learned the importance of making sure I brief the glide slope angle) and had to go missed.
We shot the approach, went missed, did a hold where we briefed the surrounding airports and our fuel (which I had taken off with appropriate IFR fuel plus some), and realized Yuma was probably the best place to go, the weather was so bad -- definite VFR. When we got there, they kept asking us to hold, giving us vectors to wait for the F38's to land, etc. I was about to declare minimum fuel at one quarter tank and one 1/8 tank. They gave us the runway just before that.
After that, I learned the importance of how planning can be real. Plan the departure, the en route, approach, the hold (x2), and a viable alternate far away from the weather (for my skillset). It's made my M20K range a lot shorter, sadly, but I've never been frightened again.
All that to say, good point and @201er could add another poll question here about what are your personal minimums for an alternate. Mine is "two alternates, far away from weather, virtually guaranteed to land at".
edit: The flight was KIWA A39 KSEE KNYL, shooting the LOC-D which is a 6.88 descent. Whew.