After booting up my computer after hibernation (suspend to disk), my desktop is unresponsive for up to 15 minutes. I've found that the slowness is caused by the fact that all running applications seem to be swapped out to disk. For example, 3 GB of RAM may be in use when I suspend to disk. After resuming from hibernation, RAM usage is low (500 MB or so) and slowly everything will start to get swapped back into RAM. The problem does not occur with sleep (suspend to ram).
I'm running Arch Linux on a Toshiba Satellite L300-2CP with 4 GB of RAM and a 4 GB swap partition.
EDIT: TuxOnIce (using the linux-pf kernel) indeed makes a huge difference, and basically solves the problem for me. I would find it hard to believe that what I was experiencing with the standard kernel (swsusp) hibernation is normal, however...
EDIT 2: Of course TuxOnIce hangs now and then during hibernation.