I've toyed with the idea of getting one solely for aviation purposes. I spoke to a guy recently that uses one for flight planning etc. I like the idea that you can get homebriefing.com on the web browser and file/delay/cancel flight plans easliy.
Also I read the other day that you can connect them to a laptop easily and use them as a 3G modem. So if you had a laptop in the plane you could use it to connect to the internet on the laptop, especially useful when abroad.
Nokia E61 is a better tool. It has a web browser on it which can be accessed with its 3G modem but also (which I thought was damn useful) if you are near a WI-FI modem you can surf the web at broadband speed on one of these little things!!