Mulivitamins have been disappointing to say the least. There is little evidence, for example, that they protect men from the big killers of heart disease and cancer. The latest slap in the face was a huge study of 162,000 women in the Archives of Internal Medicne that found no correlation between taking a multivitamin and heart disease, cancer or total mortality.  Actually, some large studies have shown cardiovascular benefits,  but this is controversial at best.
Because of studies such as these, many of those in the traditional medical establishment like to slam taking multivitamins as complete waste of money. However, I feel these criticisms are overstated, because there are several areas where multivitamins may excel for us guys. One surprising area where the evidence for multivitamins looks good is the brain.
The reasons for this are many, but suffice it to say that the brain is a huge nutrient and energy hog. It requires, among other things, lots of the B vitamins. Plus, as people age, they often lose GI acidity and the ability to digest certain vitamins, including the B vitamins, and minerals. A good multivitamin, therefore, looks like a good insurance policy for you grey matter.
There is another key area where a multivitamin may help: immunity. One study has found that a multivitamin with around a 100% of the RDA in minerals as well as vitamins can protect against colds and flus. Several studies have shown that in seniors, whose vitamin and mineral digestion has often declined, a multivitamin/mineral supplementation can help prevent infections.  This was backed up by a recent study that showed that even those in the 50-65 age range can get an immune boost as well. 
NOTE: Many cheap multivitamins have fillers such as Calcium that actually slows or halts the absorption of much of what is in the multivitamin! In addition, some of the standard multivitamins are highly compressed, which is why you could load it as a round if they put a little powder in it, and thus do not dissolve fully.
CAUTION #2: There is also evidence that too much selenium can raise cholesterol.  Men need to be careful here, because cholesterol is a risk factor for heart disease and endothelial dysufunction, which will translate to poor erections eventually. The study above showed that those with the highest selenium had 8% higher cholesterol and over half of those in this category were taking multivitamins. 
REFERENCES:1) Arch Intern Med. 2009;169(3):294-304, “Multivitamin Use and Risk of Cancer and Cardiovascular Disease in the Women’s Health Initiative Cohorts”
2) Personality and Individual Differences, 1991, 12(4):351-362; Personality and Individual Differences, 1991, 12(4):363-365
3) Am J Clin Nutr, 1997 Jan;65(1):20-9
5) Chandra RK. Influence of malnutrient supplement on immune responses and infection-related illness in 50-65 year old individuals. Nutr Res 2002;22:5-11
7) Am J Clin Nutr, 2010 Nov, 92(5):1251-6, “Multivitamin use and the risk of myocardial infarction: a population-based cohort of Swedish women”
8) American Journal of Clinical Nutrition, Aug 2008, 88(2):416-423, “Serum selenium and serum lipids in US adults”