I run as a fill in for JB Hunt(I don't go home much its the only way to run as a fill in). Basically when someone on a dedicated account needs to leave for whatever reason. I come in and fill in there spot until they find another driver. You don't need to be a vet with them to move up on the respect pole. Just need to work your butt off and realize that there will be a few bad weeks between a lot of good weeks.
If you run as you should, don't accept stuff you cant do, drive slow and safe, and have a record of almost 100% on time delivery they will treat you good. If you fudge your logs, try to get 3000 miles every week/complain when you don't, and are a bad driver in general they may just set you in a corner and let you fester until you leave.
The main reason why I work for them is that they pay tolls, they do run legal, and being a big company I don't need to worry about them paying me.
My only vice is the equipment they will get it fixed it is just something that you have when you do a lot of drop/hooks. It is more in the OTR division where driver A leaves a trailer with a flat for driver B and does not tell anyone. This is not a issue with the rail or some dedicated accounts where they have a service that comes in and inspects the equipment daily/weekly.
I am saving up to buy a house outright in about 2 years. I'm happy with this company and how they have treated me over the last 3 years. I could see myself grabbing a dedicated account through them without question when that time comes or moving into a different type of company(like propane or other haz containers) using JB and there safety background (and mine) as a spring board.