Judging by existing reviews, individual opinion seems to rely very heavily on the views of fans of the 50s TV series (i.e. old blokes like me), versus those who came in cold and took it on face value. It is important to note that the film was never intended to have any relationship to the TV version. Richard Greene, of course, starred in both... and that's about the extent of it.
The Sapphire Films television series was a whole different kettle of fish. American writers blacklisted in the McCarthy era wrote under pseudonyms and packed the first two seasons with subtle left-wing ideology. The last two seasons fell into a more formulaic adventure groove, but still managed the occasional political overtone.
The movie was typical of the Hammer production philosophy... take what little budget there was, invest heavily in production costs (vivid colour, widescreen ratios), and hire a passable cast with what's leftover (including at least one bonza babe). I'm betting Greene came pretty cheap and had the added bonus of drawing in fans of TV series.
What you see is what you get. It still looks great, the storyline is good enough to last out the whole 77min, and there isn't a political statement in sight. For mine, 6.5 stars out of ten.