Where do I even start if hibernate / un-hibernate is slow?

The official hibernate troubleshooting page is Debugging Kernel Hibernate

However, this forums article looks like it might be more useful (start at comment #4).

I think the time taken to (un)hibernate will depend mainly on the RAM and swap usage. When you hibernate, the data in RAM is basically saved into swap and when you unhibernate it is loaded from disk. This will be slower when there is more RAM to move. When some swap is used it will most likely take even longer.

It may help with speed if you close the programs which you don't need to sustain their current state before hibernating. I always shut down completely if possible.

I don't think there is an internal way to time (un)hibernation.

http://en.wikipedia.org/wiki/Hibernation_(computing)

Not only open applications, but also devices plugged in can affect hibernate time as they often have to be shut down and then brought up in just the right order and have timeouts and such applied to them. Maybe it takes longer when you've got a USB hub or printer plugged in? or when you've been using the audio device a lot?