Hibernation is a very nice feature (I use it for laptop and desktop machines) and it requires a swap partition. Also, a encrypted swap is even more important in this scenario.
In the laptop I'm typing this, swap is one of the partions over a LVM2 physical volume over LUKS.
If you do have swap, though, then the encryption probably won't matter much compared to the fact that your machine is swapping in the first place.