So far... I have only ONCE had to fully reboot (power off, power on) the 1.5 cupcake OS (?) since updating the phone.
The restart was more to do with me shutting down a ton of applications through 'Advanced Task Manager lite'. The 'End All' option... should be used only (ONLY!) when you are ready for some instability.
That makes sense to me...so, be careful when just forcing applications to shutdown.