It does, N900 can swap batteries without rebooting if you are near a wall charger or have an external emergency pack.

As for hibernate issues, they all have it. The hibernation saves as much as possible from the state of PC, like RAM, state of CPU, registers, etc. However, not everything is saved, for example internal state of hardware. On resume, the GPU might be in a mode that sucks, cards might be in a "clean" state, etc. Any driver, card, etc not working perfectly on hib will destabilize OS operation sooner or later.

For me, it's the audio card that goes odd on resume. Need to reset it every resume.

Saying that one OS or another is better is hearsay and special case scenarios. Truth is, hibernation is not feasable unless all is known. Like in a good laptop.

There are cool things afoot, like Asrock's Instant on. What it does on poweroff is reboot to a clean OS and then go in deep STR, so on button press it has a 1 sec powerup. Fails for power loss, though.