Just relating my experiences regarding Midlet signing.

Signing only really means tested on one type of mobile. What's the point of having a ceritification process for software when mobile manufacturers are free to implement the JVM any way to choose. Sometimes these implementations are so buggy, you wonder why there isn't a certification process on that end.
The testing is so basic, you are really only paying for the stamp of approval and the 'privilege' of displaying the java powered logo.
Getting rid of that dialog box is nice but not necessary. The fact that some of the best java apps out there like FreeNews has not been certified just supports that point.
My humble opinion..It's just not worth it.
First post ever .. apologies if I ve broken any rules.