There is no good reason to circumcise a boy, listen to your boyfriend he seems to know.
The cleanliness thing is simply a myth, there is no special care necessary other than occasionally giving your baby a bath from time to time and I know you'll be doing that. You just clean his penis with a quick wipe, like a finger, just clean what you see. Reference [1] will discuss the myths of cleanliness. Once a boy's foreskin is retractable, and the boy should be the one to first retract his foreskin, he can occasionally do that in the tub or shower, it take only a second. Reference [2] discusses normal development from birth to 18 and retraction.
Circumcision also doesn't really protect against STDs, the problem is that anytime a study shows a slight benefit to circumcision, it is up sold in the US media but not when the opposite results are found which occurs often.
For example, a New Zealand study was recently published in the March 2008 Journal of Pediatrics, "Circumcision and Risk of Sexually Transmitted Infections in a Birth Cohort" by N. P. Dickson, T. Van Roode, P. Herbison and C. Paul, J Pediatr 2008;152:383-7, shows that circumcision does NOT prevent STDs. These findings are consistent with recent large population-based cross-sectional studies in developed countries and found that early childhood circumcision does not markedly reduce the risk of the common STIs in the general population in such countries. Dickson followed his cohort for 32 years and found no association with circumcision an STDs. Read that one here [3].
The large studies that Dickson's results match up with include the results of an Australian study (International Journal of STD & AIDS 2006) of over 10,000 men which found found after correction for age, circumcision was unrelated to reporting STI found at: [4]
It also corroborated the results of a smaller British Study (STI 2003), a mere 2,000 men, which also did not find any significant differences in the proportion of circumcised and uncircumcised British men reporting ever being diagnosed with any STI. Found at:[5] And the results from a study of the US Navy population (XV International AIDS Conference 2004). Found at:[6]. I should add that the Navy also checked for HIV in that study and found no correlation.
In a 2005 article, Dickson et. al. also looked specifically at HSV.[7] Following a birth cohort of boys to age 26, they tested for HSV serologically and found no association with circumcision and HSV. These results were similar to a separate serological trial conducted on a clinic population India.
The link to HIV is also not relevant to boys, especially those in first world countries. For example, the Australian Federation of AIDS Organizations in their July 2007 statement said:
* “Male circumcision has no role in the Australian HIV epidemic”,
* “African data on circumcision is context-specific and cannot be extrapolated to the Australian epidemic in any way.",
* and perhaps their best observation “The USA has a growing heterosexual epidemic and very high rates of circumcision”.
Read the rest of the Australian statement here:[8]
While the French National Council on Aids (Conseil national du SIDA) in their August 2007 report concluded:
"The recommendations of the WHO state that this strategy is aimed at countries with high prevalence, and not at countries with low prevalence or in countries where it relates specifically to one part of the population such as in France or the United States." Read the rest of the French statement here[9].
Other first world countries have come to similar conclusions, and in the US context even if you believed the purported benefit up sold in the mass media, in real numbers it is vanishingly small for almost all countries.
So take your boyfriend's suggestion to heart. He has a foreskin and knows it's benefits. The vast majority of the world's men are intact and only a very small percentage ever need or want a circumcision. By leaving your boy intact you also give him options.
And not to nitpick, but even if we don't know that a part of the body has a function, that doesn't mean it doesn't. It just means we haven't figured it out yet. For instance, you mention the appendix for which we may have found it's intent[10].