Survey of s4bios support in IBM Thinkpads, please contribute?

I'm wrestling with a new T42p, trying to make s4bios based hibernation
work.  I've tried variations on creating hibernation partitions and
files, and can get bios-based hibernation to work (to a first
approximation, I haven't tested everything) if I don't load acpi, but
I can't seem to get it working under acpi.

I have a lot of second hand accounts, some that it works, some that
it's not supported, etc...

I'd like to collect folk's first hand (or very close) experiences,
I'll compile them and summarize to the list so that it actually gets
archived.

I'm *particularly* interested in T4[012]{,p} stories.

If you've tried using bios based hibernation and ACPI on a Thinkpad,
please let me know how it went, which model, which bios release, and
how you tried to set it up.

Thanks,

g.