As a former manager with this company in Southfield, I can honestly say that some of the stories you've read here are true. I worked with these guys for awhile, and they are pretty much concerned with money -- and more "looking" effective than being effective.
Do they do anything that breaks the law on a normal basis? No, not really... They do, from what I've been able to see, conform to the law [for the most part... I'll get to that in a minute.] and I don't think goes out of its way to be unlawful.
However -- its their ethics you gotta be worried about here. They have no loyalty to their entry level employees at all, period. Some of the guys under me had worked for the company for years, loyally, and received no pay raise, and was only making just over $6 an hour (this was before the new minimum wage law in Michigan, early 2008 I believe.) They'd pay guys $7 an hour, to sit in their OWN car, running THEIR OWN gasoline, to patrol places sometimes...
When my office fell on hard times, they slashed all of my office staff except for me. I lost the receptionist/office manager and the fellow manager working the office with me - and I was left to run over 200 employees, in two states, myself - working 7 days a week, 12+ hours a day for months before I finally resigned. In fact, I had to literally beg to take ONE day off to visit family for a big event; and I still couldn't get them to take *all* of my calls. They fired those guys on a Friday, with no notice to boot.
When I finally tendered my resignation, after being told I wasn't "managing my time effectively," (it was the straw that broke the camel's back -- as you'd have trouble doing it too, if you had to be in the office from 10-5PM, then go out and do inspections, AND look for new leads! You can't do the same job of three other people and expect to keep the same levels of productivity up!) they tried to talk me out of it -- obviously, as now THEY would have to pick up the slack... and I'm certain they've bad-mouthed me as a former employee, so I've stopped utilizing them on my Resume. Sure, I left with no notice, but the company didn't give me much of a choice; and in fact, I was told by my law professor that I might have a case against them for "involuntary resignation."
The only real law-breaking issue I know of, is that the owners were fined a couple of years ago for failing to pay owed-overtime, which I know for a fact they are hugely against doing... they made a capital case anytime I had any overtime on the books, as they didn't like paying it out at all. I've remained in touch with a couple of my former employees -- and indeed, I even hired a couple of friends of mine to work for me while I was there, and remained after I left; but didn't for long... because they ran into the same issues I did - ineffective management.
So just be weary... check out your employer before you sign the paperwork with 'em. While these guys are, no doubt, on the "legal" up and up, they could definitely use a compulsory ethics class or two, especially seeing as how they're a GSA contractor.