Seen it - bought it - loved it.
The 2nd series has just finished airing on ITV2, and to be honest it deserves a place on the UK's top 4 channels (I no longer include Channel 5).
Don't expect historical accuracy. They clearly have advisors that know their stuff (I think Prof Mary Beard advised on the first series, if not the second as well) , but the writers don't let accuracy get in the way of a good comedy plot device.
I enjoyed it so much, I bought both series on Apple iTunes so I could watch it back-to-back on transatlantic flights.
I give it five dead gladiators (out of 5).