I have watched a few of the films, and now had a first look at the Suchet tv series. The latter is often hit and miss, with many filler episodes. For example, while the first ever episode was ok (it'd be a really horrible idea if they didn't at least try to start with a decent plot), none of the others in that series were interesting (though I have only seen up to episode 7 now, I think).
The 60s movie adaptation of Witness for the Prosecution was very good, in my view, and (contrary to many of Christie's plots) fairly possible to pull through irl.
@EvaDK , have you watched it yet? ^_^