You can expect to live for a decade or two at more or less your current lifestyle until near the very end, while with aggressive forms of cancer we're talking more about months of extreme pain and suffering.
If you (a) use protection and (b) are taking medicine as prescribed, however, even the risk of infecting someone else isn't that high. Your viral load remains very low; I remember a study in Switzerland that suggested that two HIV-discordant monogamous partners engaging in anal sex aren't at significant risk of seroconversion even without a condom, if the HIV-positive partner uses his drugs at prescribed and there aren't compounding factors like STDs. Which isn't to say it's a good idea.
It's definitely a trade I'd make in a second, though. Then again, I've seen people waste away from leukemia and not from AIDS, so my perspective is admittedly skewed.
Edited to add: that study is most definitely not a license to have unprotected sex with someone who has HIV. Just to be clear.
the Nature has perfected the viruses as effective delivery system of genetic material ("DNA patches") into cells. We just need to produce correctly working "patches". Another example:
I haven't studied the details of the vector they used, but as a general comment HIV is a very well-understood virus, so removing its potential to infect a human should be easy to do in theory. Practice is another matter, since molecular biology is quite messy.
