How did we achieve this great result? We have many user support issues in the bug tracker and many users don’t answer questions any more. Those bugs can be closed if the last comment is a year ago asking to provide the requested information.
Many bugs have in fact been fixed since the bug has been reported and we just have not known that there is a report for this issue. Also many bugs are just for so outdated versions (4.2 or earlier) that any information provided in the report is no longer valid. Not only KWin has improved a lot but most important also the drivers.
But there is still much more work to do in the bug tracker. 200 open reports is still much more than the number of real bugs which I expect to be below 100. So give us a helping hand. Reading an open report and trying to reproduce it is not that difficult