I dug this prequel sooo much. It's rare for a prequel to work at all, yet this one managed to actually feel like it was planned this way from the beginning. GotR works both as added backstory to Spartacus season 1, and as a story in its own right. Other than the bookend scenes that would spoil the end of season 1, I could easily see it working as a season 0 watched before 1.
Knowing that there was a real Gannacus that served under Spartacus post-escape spoiled the ending a bit, but they still managed to have me guessing if they'd stick to the history or just kill him off.

Hopefully Gannacus will have resumed whoring and boozing by the time Spartacus finds him.
It's unfortunate that Whitfield was unable to continue in the lead role, but I'm still very much anticipating season 2 already.
Oh, and even for this show, that final kill got an audible, "DAAAAAAAMN!" out of me.