Hibernate (suspend-to-disk) is enabled in -current for i386+wd configurations.
You'll see a bunch of disk activity as the pages are written out after 'ZZZ'. On resume, a full kernel boot is performed, at which point (at the very end), the hibernated image is read back from disk (more disk I/O) followed by a pause (sometimes a LONG pause) while the image is unpacked on top of the resuming environment. The machine then resumes from where it suspended using the same resume mechanism as S3 (suspend-to-ram). Please see my earlier mail for FAQs and other warnings... -ml