Yes, it's still painful But not as bad as it used to be.
Damien, one of our Toolkit contiributors has written a great little article documenting some of his experiences getting his ListSearchExtender to work cross-browser. Good times!
One thing to point out is that, like anything, most of these issues are tough when you first encounter them but you quickly adapt. As you learn some of the coding practices he calls out, and start using them without thinking about it, the easier it is to write cross-browser code.