One of the serious advantages of the P800 is that it includes PersonalJava in the OS as an equal partner with native apps. This is so cool... J2ME is such a disappointment because you can't get out of the sandbox. I mean, the TipicME app shows that there's some cool stuff you can do, but there's so much MORE you could do with Java.
Look at this app I just read about at All About Symbian:
Malcom Bryant via FrEPOC has released jText. jText is a simple text editor for the P800 written in Personal Java. It will enable you to create and edit ASCII files directly on your P800.
With jText you are able to cut, copy and paste text to or from other P800 applications. You can save the information in a plain text file which can be transferred to - and understood by - any other computer.
This is awesome! It's simple, but it's in Java! That's so great. He's also got a couple more apps written up already also. I have a book about Wireless Java Programming in Symbian, but it's written mostly for the UIQ (Quartz) reference design which includes Personal Java. So it's great, if you have a P800 which supports it, otherwise it's useless (like J2ME in general).
It would rock if I could start right now programming in Java for my phone instead of messing around with C++ which I don't know very well.