I can't remember whether I've talked about this before... but since installing Ubuntu Edgy Eft I've found that my laptop (a Sony Vaio X505/CP) can magically take advantage of all of the good ACPI stuff. I can suspend to RAM and disk (hibernate) and have plenty of control over this.
Power management has long been a Windows strong point, but with this latest release it really starts to look as though Linux is catching up... but there is still a long way to go.
Once I realised that my laptop fully supported power management I began to look at my desktop machine. I was very happy to discover that I could suspend and resume with no problem at all... but only the first time around. Come the second suspend/resume attempt, the system failed to come back -- a fairly useless feature.
Since then I've been investigating how to solve it, but I didn't get very far. I've spent the last few hours playing around with BIOS settings, running through countless fscks on my data disk and generally not getting very far... until I tried a hibernate.
Hibernate is a sleep 4 (unless suspend, which is a sleep 3). In this mode the contents of the system RAM get flushed to disk, along with the state of the CPU registers. The machine is then fully powered down and could be lugged off to the other side of the world to be powered back on. Quite by fluke I discovered that this worked. So far I've had a couple of hibernate/resume cycles without any problem.
Hibernate is a great solution for now, but in the long-term, it would be nice to gain working suspend support for all systems.