The Space Shuttle marks a change of standards for US astronauts. The Shuttle provided a smooth return to Earth from orbit and the ability to choose which landing strip to arrive at. The modified 747 allowed NASA to move a Shuttle from one landing strip to a launch site and gives a good indication of the size of the Shuttle. The Shuttle provided the spacecraft equivalent of a modern heavy military truck, able to carry crew and a heavy payload. NASA was only limited on the number of launches by preparation time and funding. The crew could range from two to eight and the payload could be a large cargo of supplies and spares for the ISS, or a large satellite. Importantly, the Shuttle could link up with space objects to allow them to be repaired in orbit or placed in the cargo bay for return to Earth and repair, replacement and/or analysis.
With the grounding of the last Shuttle, a few US astronauts may be able to hitch a ride on a Russian spacecraft if the Russians have any spare capacity. There wont be any space to carry a useful payload and the fixed route is from the Russian launch site to the ISS and return. Coming back the US astornauts will come down to Earth with a bump. The mode of transport will be the spacecraft equivalent of an old Lada so NASA also comes down to Earth with a bump.