...but is the OS4 current, or is there an additional fee required to get the most current version of OS4 installed on the hard drive?
For the Pegasos II only AmigaOS 4.1 was published, which actually is the newest. I suppose you'll get the original Pegasos-II-OS4.1-CD with registration key with this Pegasos II - so can go and download all updates (1-3) from the Hyperion website for free.
EDIT: I forgot to menton that the Pegasos II is a really nice and (up to now) very reliable machine - and the perfect system to use with both MorphOS and AmigaOS (and sometimes Xubuntu - I have a triple boot system).