i havent used them but I heard they charge more and they dont do a very clean install. you get what you pay for. of course if you dont care about how they run the wires as long as it works then go there. I dont know tho I havent used them

It says on there web site that they charge $1 per item installed and the $1 install is only avalible on items that are purchased in the store 
http://www.audioexpress.com/

I completely forgot about this... when I was shopping for an alarm and getting quotes, I found that their prices were higher than the installed price at the place I go through. So, yes, they need to make up that difference somehow. According to their site the $1 is only for labor. Custom installs, parts and supplies are all extra.

I have dealt with Audio Express many times. Hell I used to work there for about 4 years. It really depends on the store on what kind of work you got. I know the store I ran. All of us installers treated the cars like they where ours. But we also fixed alot of stuff from our other stores. So not all of them are bad.
  I would ask to see their install bay. A install bay will tell you alot about someones work. If you go back there and it is all trashed and stuff laying everywhere. That usually means they dont really care about how things are done. I know my shop I hate stuff laying around. Drives me nuts. All my customers parts all have to be in certain places or it drives me nuts.

  So back to AE. LOL.. Alot of times you can catch really good deals there. You just need to watch for it. Ask to see some of there past work as well.