I have just finished the first five episodes from the new Network Video release. Since I am an American and have never seen these episodes on-air, my opinion may differ from theirs.
As this new DVD format is the one most likely to be encountered by a modern viewer, I will address that directly. The video quality of the episodes is comparable to perhaps the earliest "I Love Lucy" episodes you may have seen, or very early "Super Man" shows. Unlike them, the exterior shots are fine and they seem to have actually taken Rupert across the Channel to film them (unlike Roger Moore in "The Saint"). But the interiors are a different story. There were sometimes issues with the video transfer process and it shows in the interiors (especially Episode 1). The interior sets look very much like something put together week by week. The standing sets for his office are a bit more detailed. The sound is like a stage production recorded. Even for 1960 some of the acting is very stage-like, with unrealistic speech and exaggerated mannerisms.
So if you can get past the late 50's production quality Rupert Davies and Ewen Solon are fine and the stories seem as effective to me as modern Maigret renditions of them (I've never read the books). Most of the supporting actors are good enough.
All 52 episodes are available, so there's quite a lot to enjoy if this is your cup of tea. But I must warn you that the production values are not even vaguely comparable to a show like 1958's "Peter Gunn", much less more modern versions.
