I havnt tried the last GPE version released today, it should provide greater stability and provide bugs for some obvious errors (date picker is not working, category slector was funky)

The main issues with GPE suite is a rather complicated synchronization with desktop/cellphone. It is possible to set it up, but no gui is provided for it. And it might require manual compilation of some packages and so on. Another problem is that an alarm framework is not developed yet (Nokia has provided only simple "make a sound at specified time" capabilities) therefore Calendar does not make sounds yet.

But the basic functionality is in. Depends on your needs