Unlike most oral steroids, which are Class II steroids giving most of their anabolic effect by means other than the androgen receptor (AR), it seems that oxandrolone probably does have good binding to the AR, and is therefore a Class I steroid, while having little other effect. By itself it is considered to be a weak anabolic.
Partly this is due to its apparent lack of non-AR-mediated activity. This can be corrected of course by stacking with a Class II steroid such as dianabol, anadrol, 4-AD, or nor-4-AD: the latter two steroids require high blood levels which are not obtained by oral use of the powders.
The other part of the reason for this is that bodybuilders make unfortunate and unreasonable comparisons when judging anabolic steroids. If say 8 tablets per day does little, then the drug is pronounced useless or weak by the user. But that is only 20 mg/day, or 140 mg/week. Does 140 mg/week testosterone give much results? No. Few anabolic steroids give dramatic results at that dose. Per milligram the potency is reasonable, but each individual tablet is weak because the dosage is small.
Because of its high price, very few bodybuilders have taken large doses of oxandrolone. There is a single case in the medical literature (Forbes et al.) where it is reported that a competitive athlete self-administered 150 mg oxandrolone per day with remarkable gains. This is of uncertain credibility because unless urinalysis was done to verify that no other steroids were taken, there is no way to be certain that the athlete did not actually take more drugs than he reported. In any case, at current prices, only the quite wealthy could afford such a dose. I personally have tried 150 mg/day and considered it somewhat effective, but not dramatically so, and not a preferred regimen.
Oxandrolone does not aromatize or convert to DHT, and has a longer half life than Dianabol - 8 hours vs. 4 hours. Thus, a moderate dose taken in the morning is largely out of the system by night, yet supplies reasonable levels of androgen during the day and early evening.
Oxandrolone shares the liver toxicity problems common to 17-alkylated steroids. At one time it was thought that it did not, but both clinical and practical experience with Oxandrin has shown that at doses of 40 mg/day and higher, liver toxicity is indeed an issue with prolonged use.
Primobolan, I believe, should be considered a superior compound, offering the same activity at (usually) a lower price and without the alkylated-toxicity issue.