Batteries (almost) included
One of the main problem with modern smartphones (and the 5800 is one of them) is the duration of batteries: if you use GPS, WiFi, and so on you can find that your battery does not last enough to finish the day. In An Exhaustive Guide to Saving Your Smartphones Battery they give some hints to improve battery life. But you shouldnt be very optimistic: they way of saving it is to avoid the smart part of the phone. Unfortunately, there are nor many hints about Symbian phones. Anyway, most of the ideas are operating-system independent.