The final landing of the Discovery marks the end of an era, but I'm not all that sad about it. After all, it was just a glorified lorry. Much of what the shuttle did, such as resupplying the International Space Station, could have been accomplished with conventional rockets. Could the ISS have been built without the shuttle? I don't see why not. Even as a reusable space craft, the shuttle was limited since many systems were had to be rebuilt after every mission.
I am more sad that the shuttle is being retired with no immediate replacement in sight. It reminds me too much much of the Apollo program, which also ended with no clear direction for the future. After 50 years, we've advanced very little in manned space travel. If it were not for our robotic explorers, humans would have no presence in the Solar system at all. At our current rate of development, I am very doubtful that humans will ever visit the places that Voyager I has. Perhaps I'm being too pessimistic.