If SUN wants JavaFX run on Nokia N900 they're gonna need either Java ME or Java SE on Nokia N900. For now, SUN is merely providing an early access version of JavaFX for Windows Mobile though.

Once JavaFX is ported to Linux/x86-32 it shouldn't be too hard to port to Linux/ARM because it already is ported to WM6/ARM. Shouldn't be too hard for SUN if proprietary or official port, for community if open source, or both.

It is nice to have backwards compatibility. I've taken advantage of this before. Sometimes, it is beyond your control because you have no power over it because your employer or business partner decides the software to be used. For example, in past I had to use Java for .nl ccTLD administration. Some custom software we run is proprietary and requires Java, they cannot be rewritten (would cost too much), and it'd be nice if I wouldn't need to use a seperate device than N900 to run these. Some corporations also require usage of Java applet, with their only alternative (if there is one!) being a bad interface. For a long time my bank required Java! I need Java to get remote desktop over HTTP, too.

We all have different needs. I don't need any of the game emulators yet they're popular. LUA was useful on Diablo for me but I doubt it was much used. Regarding Java, we're not necessarily talking about out of the box which is also both related to chicken/egg, as well as legacy from non-opensource Java.

Although you said no Java ME on S60 phone I have Opera Mini 5 as my backup browser. I like to use it when roaming. I've even used Opera Mini 4.2 on S40 phones in an emergency. I don't yet how I'm going to fix this on my N900...