Nolvadex uniquely has a couple of other nice advantages: it can help some men with gynocomastia and possibly elevated prolactin. (See my page on Tamoxifen and Prolactin for more information.) It does the former due to the fact it has some anti-estrogen properties.
What will it do to male testosterone levels? Unfortunately, that has never been studied thoroughly. However, we do have clues from a 2009 study on men with mild infertility. When these men were given Nolvadex (tamoxifen), their average testosterone levels went from 496 ng/dl to 835 and 763 ng/dl after 2 and 3 months, respectively. Those are respectable 68% and 54% increases in testosterone. We had one poster on The Peak Testosterone Forum that experienced an even bigger jump on Nolvadex and more than doubled his testosterone from a baseline of about 300 ng/dl up to 700 ng/dl. 
Then why aren’t more doctors doing it? And why is Clomid so much more popular? I believe the answer may stem from the fact that Nolvadex can be hard on the liver if used in the long term. This summary is rather sobering for example:
“Tamoxifen therapy has also been linked to the development of fatty liver and steatohepatitis. In some prospective studies, up to one third of women have developed fatty liver during long term tamoxifen therapy, as shown by routine imaging using computerized tomography. Fatty liver usually becomes demonstrable within 1 to 2 years of starting tamoxifen but is usually not accompanied by symptoms, although serum aminotransferase levels may be elevated modestly in up to half of patients. Liver biopsy may demonstrate steatohepatitis and a proportion of women develop hepatic fibrosis. Several instances of cirrhosis have been described after therapy with tamoxifen for 3 to 5 years. Serum aminotransferase elevations and fatty liver generally improve once tamoxifen is stopped, but the improvement may be slow and in rare instances, signs and symptoms of portal hypertension persist.” 
Now men typically take lower dosages than a woman being treated for breast cancer. Nevertheless, I suspect many physicians will shy away from tamoxifen considering the much more liver-friendly history of Clomid. Keep in mind that Nolvadex is also associated with eye problems. According to this author, it mostly occurs with long term use in women using higher dosages:
“Tamoxifen, a triphenylethylene nonsteroid oestrogen antagonist, has been widely used as an adjuvant postoperative therapy of oestrogen receptor-positive breast cancer. Its ocular toxicities, such as retinopathy, keratopathy, optic neuritis and cataract, have been reported since 1978, and tend to occur in patients who have a higher total dose and longer treatment. These complications seldom cause significant visual impairment and, except for crystalline retinopathy, are reversible upon discontinuation of tamoxifen.” 
Nevertheless, I see regular eye exams encouraged. (Clomid can cause visual issues as well. See my page on Long Term Clomid Risks for more information.)
CONCLUSION: While it is possible to use Nolvadex to significantly raise testosterone in many hypogonadal men, it is currently not being done as far as I know. I have a Peak Testosterone Forum Poll and no one stated that they were on “Nolvadex Monotherapy.”
NOTE: Keep your eyes out for a new drug on the horizon called Androxal. It should be approved in a couple of years and is essentially a SERM, but uses isomers that are not so powerfully estrogenic in symptoms. Assuming side effects are low, it promises to be quite popular.
1) Fertility and Sterility, April 2009, 91, 4(Suppl):1427 1430, “The effect of selective estrogen receptor modulator administration on the hypothalamic-pituitary-testicular axis in men with idiopathic oligozoospermia”
3) Eye, 2003, 17:276 278, “Should we discontinue tamoxifen in a patient with vision-threatening ocular toxicity related to low-dose tamoxifen therapy?”