I don't personally use a leaf blower, but I've never been bothered with the noise from two-stroke petrol leaf blowers. It's just a part of fall.
Other people are bothered by them. It's not just the noise that bothers people, it's the sociopathic mindset that leads some people to think they can do whatever they want without consequences, because other people aren't real to them. Many human beings do not react well to aggression or perceived aggression from sociopaths: this sort of thing seems to trigger defensive responses that can cause situations to escalate in ugly ways.
In general, noise is a big problem for society, and it is a problem that is fundamentally married to technology, which is why I'm pleased to see this discussion happening on Slashdot. You will likely find issues with respect to noise in any part of the world, first world or third. Our technology lets us easily produce sound levels that can (and do) damage hearing beyond possibility of repair. It's traditionally been a bigger problem in the third world, due to unregulated work conditions and industrial noise, but rates of hearing loss among children in the first world are up 30% today from even the 1980's and 1990's.
The traditional model is that sound amplitude and duration lead to permanent hearing loss (somewhere around 80dB), but the science behind this is sketchy IMHO.
Unfortunately, even this model is not being adhered to. I find that many DJs and club managers will play music that violate the US federal laws with respect to noise in the workplace: they're not just at the limits, they're way beyond the limits. Live bands are even worse - it seems like a lot of musicians are deaf enough they don't understand how loud they are being. A decent sound level meter will measure this: I've measured a live band at over 100db, from outside a building with the doors closed, which implies a maximum exposure of 15 minutes to be compliant with US law. Given that the sounds inside are probably at least 3dB higher, that drops to 7.5 minutes!
The club managers, restaurant managers, and so forth that are allowing this to happen on their watch are being really stupid, since not only are they potentially liable under federal law (a club is a workplace), but also probably liable under state laws regarding assault and battery. One could also make an argument against this in terms of fundamental rights, from a 9th Amendment perspective.
There is hearing protection available, but it isn't clear how well it works, especially over the long term. Worse, having to wear it can be a source of stress in itself. Further, most people don't automatically carry hearing protection with them to places like restaurants.
There is now evidence that lower levels of sound can lead to serious health risks. A 2008 study by Dr Lars Jarup and others in the EU measured blood pressure increases in response to both nighttime airplane noise, and road traffic, and developed a model that suggests long term exposure to much lower sound levels (even under 50 dB, the threshold at which most people wake up) can cause stress, hypertension, increased risk of heart attack or stoke, etc.
It's almost like the human animal evolved in a dangerous environment, and as a result monitors the surroundings even when we're asleep, and can trigger initial stages of fight or flight reactions (which come with the potential for the body doing long term damage to itself), whether we consciously realize it or not!
Even before this study, there was no doubt that many people find unwanted noise in their environment annoying and stressful, which is why many places around the world have noise ordinances in residential areas (55dB is fairly common at night). Evidence has been steadily accumulating since the 1950's that long term stress has physiological consequences, which is a fancy way of saying that exposing people to it isn't very different from punching them in the face.
Noise in the workplace is also a big concern: there's a lot of equipment now that requires massive cooling, and noisy fans are being used to do that (fan sounds under 50dB are known to annoy some people). If, as the evidence suggests, lower noise levels can lead to health issues, then is a big problem from a workplace health and safety perspective. Worse, people change how they talk in the presence of ambient noise, often unconsciously. It's called the Lombard effect (1911): both amplitude and other voice characteristics change, and the net effect can make a conversation pretty annoying to other people in the vicinity (and the culprits may not realize how loud they are being, which can make a bad situation worse).
All this can be bad for ordinary people, but it's especially problematic for those with hearing disabilities. Most people understand that it wouldn't be right to steal the crutches from a crippled person, but many have problems generalizing to the idea that one has to be careful about deliberately creating noise that will cause problems for the hearing disabled.
There is also evidence that environmental noise has measurable cognitive impact. People don't seem to think as well in the presence of noise, judgement suffers, children in in portions of a school that are exposed to more external noise pretty consistently tend to have lower test scores, and so on.
In short, noise in the environment is a big problem, and we need to pay more attention to this issue. It should be addressed directly, and hence the leaf blower issue should be addressed primarily from a noise pollution issue and only secondarily from a chemical pollution issue. This doesn't mean one can't use leaf blowers at all, of course, but society needs to help people use them with better judgement and appropriate consideration for others.