I'm a suppoter of the database method that Ethank employs, and am eagerly awaiting his re-release for the 2.2.0 version, so I can go ahead with my upgrade.
Besides the fact that it is more reliable, to me at least, than using cookies, it also allows me to place "Mark Forum Read" links on the Forum index, and oh how I love redundancy and multiple ways to do the same thing.