Oldhammer... a revolt against the plastic mass produced sprues of contemporary fantasy and science fiction wargaming? A sentimental attitude harking back to the time of blister packed white metal/lead figures of our childhood? A bit of both... but its more than that.
The old lead still has a lot to give- it's hand sculpted details may be softer than the modern digital sculpted, dynamic models but it has a certain charm with the sometimes wild designs and exaggerated shapes. A lot of the sculpts seem to rely on- from what I understand- the rtv molding and spin-casting process that limits the dynamism to a degree while trying to achieve a single piece figure cast.
Artists/sculptors seemed to imbue more of their own ideas into the pieces that hinted at a much more varied universe and made for a range of interesting, diverse characters and creatures before an amalgamated style was settled upon.
There are some great blogs showcasing these old classic pieces...
In addition here is a great interview with Rick Priestly with a lot of tidbits on the conception of 40K and the 'old days'...
And in the meantime here are a few Undead pieces of mine- old and new. A mix of 80's Citadel metal, contemporary plastic from Games Workshop and Mantic and some models from the metal Lord of the Rings range.