So I was trained on Runner a few days ago. For Front desk runner you basically get to do a few different things.
The 6 am runner is responsible for delivering some of the Disney's Magical Express envelopes and the Express Check Out envelopes. Then you get a list of rooms to check to make sure they are clean and vacant. Afterwards you spend most of the day sorting and delivering character cards for guests. Every so often the back office will need you to go up to a room because the guest got locked out, or their key won't work.
The 9am runner is responsible for packages. Each piece of guest mail that comes in needs to be logged and comments need to be left on the guest's reservation or a voicemail message needs to be left on their room phone. This takes all day. It doesn't sound like it would be to difficult, but there is a lot of work involved in keeping the package log updated. Then there are floral deliveries, from the WDW Florist. They are usually pretty nice baskets, but are way overpriced. Those have to be logged and then someone has to deliver them to the room. The 9am runner doesn't get to go outside very much.
The 12:30 runner delivers the rest of the character cards/floral deliveries, and checks more rooms to make sure they are clean. Sometimes guests get to their rooms and decide they want a room change, but they have sat on the bed and used the towels and soap, so that room is now dirty.
The 4pm Runner does more things like key assists, or key deliveries, makes character cards, and stuffs the DME envelopes for the next day. If it is busy you do a lot of running around because you are the only one there from 9pm to 12:30am
You get to ride around on a Segway (once you are trained) or drive a Pargo (Which is a golf cart) I like taking the Pargo, but you kind of have to go out of the way because you can only drive it on certain paths. Sometimes you have to run from one end of property to another. Like when I was training we had to take the van over to Magic Kingdom to pick up something for a guest. That was sort of cool. We also went to some office buildings at Hollywood Studios to pick up the hotel's fastpasses for the month.
Here is my costume.
It is a short sleeved shirt, and either pants or shorts. I went for the shorts because I am always hot. The best part is that you get to wear sneakers! They have to be black, but it is so nice to wear them after wearing dress shoes everyday.
On a side note, yesterday was Easter and I made Easter Baskets for my roomies!