yeah it's a very poor oral because it isn't 17aa. so it's nicer to your liver, but it also means that if you take 100mg of it you may only get 10mg into your bloodstream and that 10mg would be back out of your bloodstream in a few hours.
it's like taking Andriol, it gets some in your bloodstream but for a male the effects are VERY weak. you'd get more out of 20mg anavar than a bodybuilding dosage of primo tabs.
so yes they work. i think they are popular with female bb'ers, but even then i think anavar is preferred.
for example if i ran a primo tabs cycle at 150-200mg/day i wouldn't expect more than 5 pounds off a 6 week cycle.
i'll put it this way, if they were given to me (FREE) i would only take them if i couldn't get anything else, honestly you'd get better results from a pro-hormone.