My dad has been an aircraft mechanic for about 25 years. He's been bouncing around different airlines the last few years and just left a company that is similiar to Skybus.
These small airline companies that are getting bigger and offering super low fees are not an airline I would fly with.
To begin with, alot of them use older corporate jets. These are planes that are made to fly on corporate schedules: the plane takes people across the country, sits for a couple days while they have a meeting or whatever, then flies them back home and sits until they have to go somewhere again.
These companies are using these planes to fly commercial schedules which means they more or less work non-stop with their only downtime being when they are having maintenance performed.
They push these planes to the absolute limit. Operating an airline is not cheap and their main revenue comes from the ticket holders. If you are getting a ticket for practically nothing then that company has to make up for it in volume. That means the company is going to put off fixing things on the planes for as long as they can because they can't afford to have a plane get grounded for repairs.
Planes have maintenance record that stays with them wherever they go. So if a pilot reports a problem after he lands, the mechanics inspect it, and if it is serious enough they fix it. But if it isn't something that immediately effects the plane's ability to fly safely, they may just write it off, in which case the plane goes to it's next destination where the next set of mechanics will look at it. The management for these small companies puts pressure on the mechanics to write as many problems off for as long as they can. The mechanics employed now are also being worked to death because these companies all offer low pay and crappy benefits so they are all having hard times finding good people. My dad quit for these reasons. He was working 18 hour shifts several days in a row every week. One of his managers even ended up having a heart attack because the poor guy was on call 24/7 and had to go in whenever he was needed.
All of this means that you have planes not originally made to handle the stresses of commercial flight, that are having their maintenance put off for as long as possible, and being worked on by overworked and overstressed employees.