Pros
Nobody is looking over your shoulder. You are on your own. Longer deliveries usually pay pretty decent. This job can fit in nicely if you have your own small business besides (selling insurance, etc that can be done flexibly). From what I've heard, Reliable Runners actually pays drivers a little bit more than most courier services.
Cons
Inaccuracies with pay. Big one here. You better write down every single delivery and the pay as soon as you do it because in 2 years I don't think they ever got back-to-back paychecks right. There is some incompetence within the brick and mortar walls of RR. Tons of miles on your vehicle. They will call you any given day of the week at any given time to ask you to do deliveries, saying "I'm in a real pickle here! Can you help?"