For those who buy loud gennies and think that putting them behind a vehicle or a little bit away from people makes them quiet enough, it does NOT. There is a huge difference between a loud bike going by on a track periodically, and the long, droning annoyance of a genny that is not quiet. It may make you feel better to say it, but yes, it IS that bad. Even a Honda or Yamaha running nearby all day is slightly annoying - notice the relief when it gets shut down at day's end.
So, if you can't lay out for the more expensive units (which are probably better values, but if you can't lay out the cash, you can't), why would you not go the extra step and build a quiet box for it? There are a ton of plans on the interweb, and they are made from cheap materials, and can even be broken down to store easily. Goes a long way to being a good neighbor.
I like this plan:
http://soundproofing.org/images/soundbox.jpg (my understanding is it's based on the principal that air goes around corners well, but sound doesn't)
I'm on the fence about which way to go. In the end, I typically prefer to buy a good quality, and just shop aggressively on price, if service is relatively equal, so I'll probably wind up with a YamaHonda. I might build the box anyway, so I can nap in the pits, right next to it
Dan B