A person should always carry a heavy machine by the bottom of the case using both hands. The handle on the top is good for lifting the top. But we don't always carry them that way.
As shown in the thread above that Quilt Novice posted the link to, I rebuild the cases. All it takes is time, effort, glue, some 1/4" plywood for the bottoms, some paneling nails and something to cover it with. It's not easy, it is time consuming, but when done they look pretty nice. So I think the end results are worth the effort.
Here's a couple more threads to look at:
{
http://www.quiltingboard.com/vintage...d-t200795.html }
{
http://www.quiltingboard.com/vintage...x-t202882.html }
I don't like the plastic cases, so I'd rather spend some money for supplies and fix an old case then buy a new plastic one.
Joe