It is a bus that you get on with seat space smaller than an airplane's, and that gets you to remote destinations for less money, but more time. If you make a reasonable income, you should probably never take Greyhound. The stations are stereotypical in that they are cast in a dank concrete, and filled with rather unsavory characters. Bus depots look like bus depots the world over, except for Vancouver, which strangely has a rather lovely one. Vancouver is also a 14 hour bus ride from Canada making it unlikely that I will ever see again.
Calgary's station is one of the uglier ones in Canada, barring Ottawa and Toronto. However, it has recently been given access to the westbound c-train line, something that our airport currently does not enjoy. This increases its overall convenience, which might make up some of the ground the building has lost aesthetically. The last time I took Greyhound, I saw a man sleeping with his head in a backpack.