I use all three. Just really depends on my mood, hibernate can be a bitch when you have tons of ****** running so sometimes I put it in standby. I shutdown the system when I don't need anything running or to continue running when I use it again.
I believe if I'm going on a plane, before going into the airport, I either put the laptop in standby or hibernate, long wait, hibernate otherwise standby (despite standby consuming little battery life). Just all depends. Standby is very stable on my IBM T42 and my built desktop systems, but standby on my sony vaio laptop and dell desktops, it's really a luck of the draw. I'd say 50% of the time on those systems, it will never come back which totally sucks.