Granted, you're paying for addresses pooled among hosts with failover, which could be well worth paying for.
But come on Linode, a single IPv6 address allocation is ridiculous.
Update: Found this post by caker (linode guy) http://forum.linode.com/viewtopic.php?t=7055&highlight=i...
He mentions a third option involving a /64, does not mention if it will cost extra:
"We'll also be rolling out support to have an entire /64 routed to one of your IPv6 Linodes, which you can then route wherever you please."