Certainly when you report issues through http://bugreport.apple.com Apple listens far more than pretty much any other company I've reported issues to, especially Microsoft (who just claim most bugs are "by design", or if they are reported in the wrong place they won't move them).
Personally I haven't had any real issues with Leopard on my MacBook, except possibly the Mail "ping" issue (mentioned above). I think a lot of people with problems might find an Archive and Install of Leopard would clear some of them up.
Thank you for this gem. Most people chose the simple UPGRADE option to install Leopard. It is impossible for Apple to know what hardware, software, and system configurations you have running. Which is why in the installation manual they recommend choosing ERASE AND INSTALL or ARCHIVE AND INSTALL. Hey, but who reads anything these days. I chose the ease method which meant I had to spend time installing previous apps and loading files, but I've never had one problem with Leopard on any of my machines.