I thought Blackadder Back and Forth was quite funny, actually.
I'm on of those guys who loves Rowan Atkinson when he's (a) playing an intelligent and conniving character and (b) playing a part written by Ben Elton. I really dislike Mr Bean, Johnny English and any part where he plays someone stupid who mugs for the camera.
I like 'Blackadder Back and Forth', too. But I am always a little uncomfortable with the idea of making a television series into a movie, Serenity notwithstanding. And Blackadder has been off the air for so long.
I didn't like BA Back & Forth because it seemed to borrow jokes from that episode of the Simpsons where Homer travels back & forth through time. Some bits were funny, like the Shakespear bit. But a lot was just 'eh' IMHO (like the whole Robin Hood thing).
Like his Johnny English - most of it was just stuff borrowed from Get Smart!. The only part I liked about the film was when he accidently shoots that secretary with the dart gun, and you see the paramedics and such show up in the background.
This could be promising, but I will allow for the problems of movies based on TV shows to not expect too much. Agree that Rowan Atkinson is better when he gets away from the mugging into the camera stuff, I still really like the school roll call routine he did at the Secret Policeman's Ball.