I've seen the trailer for s5, but not gone out of the way looking for spoilers. I tend to agree - to be honest, it seems that s1 was the best and after that it goes downhill. I'm hoping that it won't be as bad as it looked from the trailer - too much action and Gwen.
I really should finish watching Camelot at some point - I thought it was okay, some good features, some bad - but I like Arthurian retellings that aren't high medieval, so it got points for that. ;)