When it starts to be jerky/slow start x terminal and run command top and monitor processes that are on top. Is something taking over 10% cpu constantly?

.edit
And about apps. Please bear in mind following:
Maemo.org repository apps are not QA by Nokia (even thought it seems that Nokia is actually providing even worse QA on some of their ovi store apps) But ANYTHING you install to it is after all on your responsibility. YES community says that extra is safe and extra-testing/devel are for people who like to flash and report about problems, but still this is open. e.g. if you install app to windows and update win with sp3 and app brakes and affects windows performance it´s a bit 3rd part responsibility and on the other hand windows maintainers responsibility. So try to understand that freedom here means that actually quality(bugs regarding memory issues and performance issues) of apps might be weaker than on e.g. apple store where they probably test software quite troughtfully and have closed environment for apps to run.