The iTunes release is available in both standard and HD versions. An iTunes exclusive bonus feature, The Making of the Team Cawkes Painting, is included when you purchase the entire season. The Season 4 DVD is $10.99 on Amazon; the iTunes version is only $9.99 for HD, or $5.99 for standard edition.
And if you happen to be looking for something to read rather than something to watch, The Guild has also released a new one-shot comic titled Vork. Written by Day and actor Jeff Lewis, who plays Vork in the series, this comic centers around Vork and his role within both the game world and real life. As with all Guild comics, the story takes place before the events in Season 1 of The Guild. The comic's only $3.50 from Dark Horse, and you can choose one of two variant covers: Darick Robinson's gladiatorial version of Vork, or the more simplistic, real-life Vork styling of Gilbert Hernandez.
For more on The Guild, you can check out the entire series on MSN.