I just did a few file transfers via SCP from my desktop to a VPS I have. What a weird feeling--directly accessing a computer with no port forwarding.
IPv6 is supposed to get rid of the end-to-end breakage nonsense of NAT, so these are PUBLIC addresses (although dynamic). NAT is such a hack...
Even with scp, I saturated my uplink at 1MBit/s. Not sure what I hit when transferring a file back to the desktop because it transferred too fast.
I think it's safe to say that performance on a VPN would be reasonable, if not the full 10MBit/s download. (Remember, pulling a file *from* your home computer is using your lower-speed uplink, not your downlink.)
Keep in mind that you're gonna have to reconsider how you think of firewalling, security, etc. There are no private addresses on IPv6. (Well, there are, but, there aren't.) Each of your machines should have an IPv6 firewall on them and your border router should have one too.